GNU Serveez

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GNU Serveez

This manual documents GNU Serveez 0.3.1, released 11 December 2021.

GNU Serveez is a server framework. It provides routines and help for implementing IP-based servers (currently TCP, UDP and ICMP). It supports named pipes for all connection-oriented protocols.

We think it is worth the effort because many people need server functionality within their applications. However, many people experience problems with select(2) or poll(2) loops, and with non-blocking operations.

GNU Serveez demonstrates various aspects of advanced network programming in a portable manner. It is known to compile and run on GNU/Linux systems, as well as on other 32-bit and 64-bit flavours of Unix and on Microsoft Windows (9x/ME/NT/2000/XP).

You can use it for implementing your own servers or for understanding how certain network services and operations work.

The package includes a number of servers that work already: an HTTP server, an IRC server, a Gnutella spider and some others. One of the highlights is that you can run all protocols on the same port. The application itself is single threaded but it uses helper processes for concurrent name resolution and ident lookups.

Table of Contents

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1 Using Serveez

We know, you usually don’t read the documentation. Who does. But please, read at the very least this chapter. It contains information on the basic concepts. Larger parts of the manual can be used as a reference manual for the various servers.

1.1 Building and installing

1.1.1 Rebuild the package from the sources

You can skip this section if you are familiar with the GNU’ish way of configuring, compiling and installing a GNU package. Getting the source

Serveez can be found on, on one of the mirrors ( or at its original location Requirements

Serveez needs GNU Guile (Ubiquitous Intelligent Language for Extensions). The current version of Serveez is known to work with Guile 1.3 and later. Guile can be downloaded at

When installing Guile, consider specifying to its configure script options along the lines of:

--enable-static --disable-shared
--disable-arrays --disable-posix
--enable-networking --disable-regex
--without-threads --enable-ltdl-convenience

This option set is tuned for Guile 1.4 and may or may not work for your particular installation; you may need to experiment a bit. Most important is that the program ‘guile-config’ be findable in a directory named in the PATH environment variable. If not, configuration will fail with message “Guile not found”. Installation

Unpack the distribution tarball:
sleepless ~> gzip -cd serveez-0.3.1.tar.gz | tar xvf -
Change into the source directory:
sleepless ~> cd serveez-0.3.1
Configure the source package for your system:

Normally, this is done by running the configure script in the top-level directory. GNU Serveez needs a reasonably conformant C99 compiler to build. If the configure script is not able to automatically find and enable such a compiler, you can specify it directly using the ‘CC’ command-line option. For example:

sleepless ~> ./configure --prefix /gnu CC='/gnu/bin/gcc'

Note that in this example you can achieve the same results by making sure /gnu/bin is in the PATH env var.

In previous Serveez releases, the configure script had some builtin compiler flags for warnings and optimizations, conveniently exposed via command-line options. These are no longer available; instead, you can use CFLAGS for such purposes (see below). Here is a complete list of the configure script options. The list of known options can the obtained via ‘./configure --help’.


All of the debug messages (debug: some annoying crap text) can be suppressed by setting the debug level (-v). If you do not want these messages built in at all then disable this feature.


If you enable this feature the control protocol will be supported by Serveez. This protocol is for remote control of the server.


Enabling this feature tells the software package to support the IRC (Internet Relay Chat) protocol.


This feature is only available if you enabled the IRC protocol. If you enabled both of them then Serveez will support the so called TimeStamp protocol, which is an EFNet extension of the original IRC protocol. In order to connect to EFNet you MUST use this option.


When using Serveez as part of the textSure (C) chat system you will will have need of an additional web server. This option makes Serveez support a simple HTTP protocol.


If you enable this feature Serveez will support a simple built-in flood protection. It is always useful to protect the software from flood clients.


When compiling under M$-Windows the DIR argument specifies the path to the extra MinGW32 library and header files. If you want the final executable to use the Cygwin project’s cygwin1.dll instead, you have to disable this option by passing the configure script ‘--without-mingw’ or ‘--with-mingw=no’.


This option enables support for a simple network time protocol server.


If the target system supports poll and this feature is enabled the main file descriptor loop is done via poll. This helps to work around the (g)libc’s file descriptor limit. Otherwise Serveez always falls back to the select system call.


This option enables the use of the sendfile system call. Disabling it using ‘--disable-sendfile’ provides a work-around for bogus implementations of sendfile.


If you do *not* want the Gnutella spider client compiled in you need to *disable* this option.


This option tells Serveez to process any passwords as crypted.


If you enable this feature the port forwarder will be included. This is useful if you plan to use Serveez as a gateway or firewall workaround.


By enabling this you will get a fake ident server included in the binary executable.


If you enable this feature the user is able to write servers using Guile.


This includes the program passthrough server in the Serveez binary. The server provides basic inetd functionality.


If Serveez is unable to detect the correct list of local network interfaces (‘serveez -i’) you can disable this option and setup them manually in the configuration file.


This option depends on ‘--enable-debug’. With the debugging option disabled there is also no support for heap counters. The heap counters are used to detect memory leaks in Serveez.


This causes ‘make install’ to also copy libserveez and its header files to $(libdir) and $(includedir), respectively. While Serveez is in alpha (version less than ‘0.8.0’), this option is disabled by default.

For maximum flexibility and reproducibility, we recommend enabling warnings and optimizations specifying CFLAGS as a command-line option to the configure script. For reference, here is the collected set of flags built into previous Serveez releases:

  -W -fullwarn -pedantic -ansi
  -Wall -Wcast-align -Wstrict-prototypes
  -Wformat -Wno-unused -Wno-long-long

  -O2 -fomit-frame-pointer -fstrength-reduce
  -funroll-loops -finline-functions
  -fexpensive-optimizations -fcaller-saves
  -frerun-loop-opt -foptimize-register-move
  -ffunction-cse -fpeephole -momit-leaf-frame-pointer
  -fschedule-insns2 -m486 -march=pentiumpro -O3

Note that not all flags may be compatible with your compiler or even each other. That’s one of the reasons we no longer take this approach. See Defining Variables in The Autoconf Manual.

sleepless ~/serveez-0.3.1> ./configure \
  CFLAGS='-g -O3 -Wall -Wextra'
Now compile the package:
sleepless ~/serveez-0.3.1> make
Install serveez:

You must have root privileges if you want to install the package in the standard location /usr/local or in any location that is only writable by root.

sleepless ~/serveez-0.3.1> make install

If you have problems building the package out of the box this is due to GNU libtool’s inability to handle dynamic linking in most cases. That is why we recommend to try to configure the package with ‘--disable-shared’.

1.2 Environment variables

When using the serveezopt package or playing around with the dynamic server module loader of Serveez you can tell the core API of Serveez (which is the libserveez.[so|dll] library) to use an additional load path to find these server modules. The environment variable ‘SERVEEZ_LOAD_PATH’ holds this information. You can set it up via:

  on Unices
sleepless ~> export SERVEEZ_LOAD_PATH=/home/lib:/usr/local/lib

  or on Windows

1.3 Starting Serveez

When Serveez is started it reads its configuration from a file called serveez.cfg in the current directory and runs the server loop afterwards. Press ^C to abort the execution of this program. Serveez is not interactive and does not automatically detach from the terminal.

1.4 Command line options

-h, --help

Display this help and exit.

-V, --version

Display version information and exit.

-L, --list-servers

Display prefix and description of each builtin server, one per line, and exit. If Serveez was configured to include the Guile server (see Building and installing), the output includes an additional line:

(dynamic)      (servers defined in scheme)
-i, --iflist

List local network interfaces and exit.

-f, --cfg-file=FILENAME

File to use as configuration file (serveez.cfg).

-v, --verbose=LEVEL

Set level of logging verbosity.

-l, --log-file=FILENAME

Use FILENAME for logging (default is stderr).

-P, --password=STRING

Set the password for control connections. This option is available only if the control protocol is enabled. See Control Protocol Server.

-m, --max-sockets=COUNT

Set the maximum number of socket descriptors.

-d, --daemon

Start as daemon in background.

-c, --stdin

Use standard input as configuration file.

-s, --solitary

Do not start any builtin coserver instances.

1.5 Configuring Serveez

As noted above Serveez is configured via a configuration file which is by default serveez.cfg and can be set by passing the ‘-f’ command line argument. When you pipe a file into Serveez or pass the ‘-c’ argument on the command line the input stream will be used as configuration file no matter whether you passed a ‘-f’ command line switch or not.

To make configuring more fun we did not invent yet another configuration file format. Instead we use a dialect of the Scheme programming language called GNU Guile ( There is no need to be worried if you are not a programmer. What you have to do is really simple and this document shows you everything you need to know. We also provide many examples. However there are some simple concepts you have to understand. The following paragraphs will explain them.

The idea of the configuration file is this: Serveez starts, runs the configuration file (other applications usually just read them and remember the settings) and finally enters its main loop doing the things you wanted it to.

There are three things you have to do in the configuration file.

1.5.1 Define ports

A port (in Serveez) is a transport endpoint. You might know them from other TCP or UDP server applications. For example: web servers (HTTP) usually listen on TCP port 80. However, there is more than TCP ports: we have UDP, ICMP and named pipes each with different options to set. Every port has a unique name you assign to it. The name of the port is later used to bind servers to it.

The following examples show how you setup different types of port configurations. You start to define such a port using the procedure define-port!. The first argument specifies the name of the port configuration. The remaining argument describes the port in detail. Port configuration items

This table describes each configuration item for a port in Serveez. Note that not each item applies to every kind of port configuration.

proto (string)

This is the main configuration item for a port configuration setting up the type of port. Valid values are ‘tcp’, ‘udp’, ‘icmp’, ‘raw’ and ‘pipe’. This configuration item decides which of the remaining configuration items apply and which do not.

port (integer in the range 0..65535)

The port item determines the network port number on which TCP and UDP servers will listen. Thus it does not make sense for ICMP and named pipes. If you pass ‘0’ Serveez will determine a free port in the range between 1 and 65535.

recv (string or associative list)

This item describes the receiving (listening) end of a named pipe connection, i.e., the filename of a fifo node to which a client can connect by opening it for writing. Both the recv and send item apply to named pipes only. The value can either be an associative list or a simple filename. Using a simple filename leaves additional options to use default values. They deal mainly with file permissions and are described below.

send (string or associative list)

This item is the sending end of a named pipe connection. It is used to send data when the receiving (listening) end has detected a connection. The following table enumerates the additional options you can setup if you pass an associative list and not a simple filename.

name (string)

The filename of the named pipe. On Windows systems you can also specify the hostname on which the pipe should be created in the format ‘\\hostname\pipe\name’. By default (if you leave the leading ‘\\hostname\pipe\’ part) the pipe will be created on ‘\\.\pipe\name’ which refers to a pipe on the local machine.

permission (octal integer)

This specifies the file permissions a named pipe should be created with. The given number is interpreted in a Unix’ish style (e.g., ‘#o0666’ is a permission field for reading and writing for the creating user, all users in the same group and all other users).

user (string)

The file owner (username) of the named pipe in textual form.

group (string)

The file owner group (groupname) of the named pipe in textual form. If this item is left it defaults to the file owner’s primary group.

uid (integer)

The file owner of the named pipe as a user id. You are meant to specify either the uid item or the user item. Serveez will complain about conflicting values.

gid (integer)

The file owner group of the named pipe as a group id. This item defaults to the file owner’s primary group id. You are meant to specify either the gid item or the group item. Serveez will croak about conflicting values.

ipaddr (string)

This configuration item specifies the IP address (either in dotted decimal form e.g., ‘’ or as a device description which can be obtained via ‘serveez -i’) to which a server is bound to. The ‘*’ keyword for all known IP addresses and the ‘any’ keyword for any IP address are also valid values. The default value is ‘*’. The configuration item applies to network ports (TCP, UDP and ICMP) only.

device (string)

The device configuration item also refers to the IP address a server can be bound to. It overrides the ipaddr item. Valid values are network device descriptions (probably no aliases and no loopback devices). It applies to network ports (TCP, UDP and ICMP) only.

A note on device bindings: Device bindings are based on the SO_BINDTODEVICE socket layer option. This option is not available on all systems. We only tested it on GNU/Linux (2.2.18 and 2.4.17 as of this writing). Device bindings are very restrictive: only root can do it and only physical devices are possible. The loopback device cannot be used and no interface alias (i.e., ‘eth0:0’). A device binding can only be reached from the physical outside but it includes all aliases for the device. So if you bind to device ‘eth0’ even ‘eth0:0’ (and all other aliases) are used. The connection has to be made from a remote machine. The advantage of this kind of binding is that it survives changes of IP addresses. This is tested for ethernet networks (i.e., eth*) and isdn dialups (i.e., ippp*). It does not work for modem dialups (i.e., ppp*) (at least for Stefan’s PCMCIA modem). The problem seems to be the dialup logic actually destroying ppp*. Other opinions are welcome. Device bindings always win: If you bind to ‘*’ (or an individual IP address) and to the corresponding device, connections are made with the device binding. The order of the bind-server! statements do not matter. This feature is not thoroughly tested.

backlog (integer)

The backlog parameter defines the maximum length the queue of pending connections may grow to. If a connection request arrives with the queue full the client may receive an error. This parameter applies to TCP ports only.

type (integer in the range 0..255)

This item applies to ICMP ports only. It defines the message type identifier used to send ICMP packets (e.g., ‘8’ is an echo message i.e., PING).

send-buffer-size (integer)

The send-buffer-size configuration item defines the maximum number of bytes the send queue of a client is allowed to grow to. The item influences the “send buffer overrun error condition”. For packet oriented protocols (UDP and ICMP) you need to specify at least the maximum number of bytes a single packets can have. For UDP and ICMP this is 64 KByte. The value specified here is an initial value. It is used unless the server bound to this port changes it.

recv-buffer-size (integer)

The recv-buffer-size configuration item defines the maximum number of bytes the receive queue of a client is allowed to grow to. The item influences the “receive buffer underrun error condition”. The value specified here is an initial value. It is used unless the server bound to this port changes it.

connect-frequency (integer)

This item determines the maximum number of connections per second the port will accept. It is a kind of “hammer protection”. The item is evaluated for each remote client machine separately. It applies to TCP ports.

allow (list of strings)

Both the allow and deny lists are lists of IP addresses in dotted decimal form (e.g., ‘’). The allow list defines the remote machines which are allowed to connect to the port. It applies to TCP ports.

deny (list of strings)

The deny list defines the remote machines which are not allowed to connect to the port. Each connection from one of these IP addresses will be refused and shut down immediately. It applies to TCP ports. TCP port definition

Definition of a TCP port configuration with the name foo-tcp-port. The enhanced settings are all optional including the ipaddr property which defaults to ‘*’. The ipaddr item can contain any form of a dotted decimal internet address, a ‘*’, ‘any’ or an interface description which you can obtain by running ‘serveez -i’.

(define-port! 'foo-tcp-port '(
    ;; usual settings
    (proto  . tcp)              ;; protocol is tcp
    (port   . 42421)            ;; network port 42421
    (ipaddr . *)                ;; bind to all known interfaces
    (device . eth0)             ;; bind to network card

    ;; enhanced settings
    (backlog           . 5)     ;; enqueue max. 5 connections
    (connect-frequency . 1)     ;; allow 1 connect per second
    (send-buffer-size  . 1024)  ;; initial send buffer size in bytes
    (recv-buffer-size  . 1024)  ;; initial receive buffer size in bytes

    ;; allow connections from these ip addresses
    (allow             . (

    ;; refuse connections from this ip address
    (deny              . (
  )) Pipe port definition

Definition of a pipe port configuration with the name foo-pipe-port. When bound to a server it creates the receiving end and listens on that. If some client accesses this named pipe the server opens the sending end which the client has to open for reading previously.

The only mandatory item is the file name of each pipe. If you want to specify a user creating the named pipe (file ownership) use either the user or the uid setting. Same goes for the items group and gid.

(define-port! 'foo-pipe-port `(
    (proto . pipe)                   ;; protocol is named pipe

    ;; specify the receiving endpoint
    (recv . ((name . ".foo-recv")    ;; name of the pipe
             (permissions . #o0666)  ;; create it with these permissions
             (user . "calvin")       ;; as user "calvin"
             (uid . 50)              ;; with the user id 50
             (group . "heros")       ;; which is in the group "heros"
             (gid . 100)))           ;; with the group id 100

    ;; specify the sending endpoint
    (send . ((name . ".foo-send")
             (permissions . #o0666)
             (user . "hobbes")
             (uid . 51)
             (group . "stuffed")
             (gid . 101)))
   )) ICMP port definition

Define an ICMP port configuration which will accept connections from the network interface ‘’ only and communicates via the message type 8 as described in the Tunnel Server chapter. The name of this port configuration is foo-icmp-port. When you are going to bind some server to this kind of port you have to ensure root (or Administrator under Windows) privileges.

(define-port! 'foo-icmp-port '((proto  . icmp)
                               (ipaddr .
                               (type   . 8))) UDP port definition

Simple definition of a UDP port configuration with the name foo-udp-port.

(define-port! 'foo-udp-port `((proto . udp)
                              (port  . 27952)))

1.5.2 Define servers

A server (in Serveez) is a snippet of code that implements some protocol. There are many servers built into Serveez but you can implement your own, too. For example we provide a webserver implementing the Hypertext Transfer Protocol (HTTP). Each server has a different set of options you can change. You can have many instances of every server, each with a different set of options. For example: You can create a webserver on TCP port 42420 publishing the Serveez documentation and also have another webserver on a different port publishing something else. Every server has a unique name you assign to it. The name of the server is later used to bind it to a port.

The following example instantiates a server with the short name “foo”. Each server in Serveez has got a short name. See Existing servers, for the details. This example demonstrates everything which is possible in server configurations. You start a definition of a server with the procedure define-server!. The following argument specifies the name of the server instance (in this case foo-server) which starts with the short name. The second argument describes the server in detail. Each configuration item is setup with a (key . value) pair where key is the name of the configuration item and value is the value which depends on the type of the item. See Some words about server configuration, for a detailed description of each type of value.

(define-server! 'foo-server '(
    (bar . 100)                             ;; number
    (reply . "Booo")                        ;; character string
    (messages .                             ;; list of strings
      ("Welcome to the foo test server."
       "This one echos your lines."))
    (ports . (5 6 7 8 9))                   ;; list of numbers
    (port . foo-tcp-port)                   ;; a port configuration
    (assoc . (( "GNU" . "great" )           ;; associative list
              ( "Tree" . "tall" )))
    (truth . #f)                            ;; boolean value

Serveez provides a number of server types. Each of them has a short name. The name of the server instance has to begin with this short name followed by a dash (-). You can append any suffix then. In the example above “foo” is the short name and foo-server the name of the server instance.

1.5.3 Bind servers to ports

Finally you can bind servers to ports. When you do so the server you created listens on the port, accepts connections and serves clients. It does so as soon as Serveez enters its main loop right after running the configuration file. Serveez won’t stop until you interrupt it (e.g., by pressing ^C in the terminal you started it in).

This example binds the server foo-server (s.a.) to the port foo-tcp-port which was described above. Therefore you need to call the procedure bind-server! which takes two arguments specifying the name of a port configuration and a server instance. Both need to be defined before you can write this statement.

(bind-server! 'foo-tcp-port 'foo-server)

One of the main features of Serveez is that you can bind multiple servers to the same port. This for example is useful to pass braindead firewall configurations or proxy servers. It is also possible to bind servers to ports they are actually not designed for. This might be used for debugging servers or other funny things (again, think about the firewall). This is the point we have to warn you: Some protocols cannot share the same port (e.g., the tunnel server) and some protocols simply won’t work on ’wrong’ ports. Additionally, you will not get error messages when that happens. The server just will not work then.

1.5.4 Additional configuration possibilities

The three procedures define-port!, define-server! and bind-server! return #t on success and #f on failure. For your convenience we provide some more built-in procedures, some of which are based upon those above. output

Scheme Procedure: fs s [args…]

Return a string made by applying simple-format #f to s and args. For example:

(fs "~A-~S" 'foo 42)
⇒ "foo-42"
Scheme Procedure: println [object…]

Do display on each object. Then, output a newline.

Scheme Procedure: printsln spacer [object…]

For each object, do display on it and on spacer, as well. Then, output a newline. augmenting

Scheme Procedure: interface-add! interface

Add interface to the list of known network interfaces. You can get the list of known interfaces by running the shell command ‘serveez -i’. The interface argument must be in dotted decimal form (e.g., ‘’). Serveez provides this procedure for systems where it is unable to detect the list of network interface automatically.

Scheme Procedure: loadpath-add! [dir…]

Append dir… to the server modules load path.

Scheme Procedure: serveez-load filename

Try to load filename (via primitive-load). If filename is not absolute, search for it in the list of directories returned by serveez-loadpath. Return #t if successful, #f otherwise. abstractions

Scheme Procedure: bind-servers! [args…]

Bind all servers and ports in args to each other. This is a cross-product operation; given s servers, and p ports, s * p bindings will be created.

Scheme Procedure: create-tcp-port! basename port

Define a new TCP port named by concatenating basename and port. Return the new name.

Scheme Procedure: bind-tcp-port-range! from to [servers…]

Bind the list of servers to simple TCP port configurations whose network ports range between from and to both inclusive.

Scheme Procedure: create-udp-port! basename port

Define a new UDP port named by concatenating basename and port. Return the new name.

Scheme Procedure: bind-udp-port-range! from to [servers…]

Bind the list of servers to simple UDP port configurations whose network ports range between from and to both inclusive. rpc

Scheme Procedure: getrpcent

Return the next RPC entry as a vector of the form: #(name aliases program-number). name is a symbol, aliases is a list (possibly empty) of symbols, and program-number is an integer. If the list is exhausted, return #f.

Scheme Procedure: getrpcbyname name

Return the RPC entry for name, a string. (FIXME: Should be able to handle a symbol, too.) If no such service exists, signal error.

Scheme Procedure: getrpcbynumber number

Return the RPC entry for number, an integer. If no such service exists, signal error.

Scheme Procedure: setrpcent [stayopen]

Open and rewind the file /etc/rpc. If optional arg stayopen (an integer) is non-zero, the database will not be closed after each call to getrpc (or its derivatives getrpcent, getrpcbyname, getrpcbynumber).

Scheme Procedure: endrpcent

Close the file /etc/rpc. misc

Scheme Procedure: serveez-verbosity [level]

Return the verbosity level (an integer). Optional arg level means set it to that level, instead. This setting is overridden by the command-line ‘-v’ option.

Scheme Procedure: serveez-maxsockets [max]

Return the maximum number of open sockets permitted (an integer). Optional arg max means set it to that number, instead. This setting is overridden by the command-line ‘-m’ option.

Scheme Procedure: serveez-passwd [pw]

Return the control password (a string). Optional arg pw sets it to that, instead. This effectively does nothing if the control protocol is not enabled.

We now have a closer look at the internals of Serveez. If you are not interested in that have a look at the existing servers (See Existing servers.).

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2 Concept

2.1 Overall concept

The primary functionality Serveez provides is a framework for Internet services. It can act as a kind of server collection and may even replace super-servers such as the inetd daemon.

Its key features and benefits are:

  • support for packet and connection oriented protocols
    Serveez currently supports two server types. TCP and named pipe servers are connection oriented servers. This type of server accepts a client’s connection request and communicates with it using a dedicated connection. The format of the incoming and outgoing data streams are irrelevant to Serveez. Packet oriented servers (like UDP and ICMP) receive data packets and respond to the sender with data packets. A server in Serveez can detect whether it is bound to a packet or connection oriented port configuration and thus can act as the expected type.
  • server and client functionality
    Besides a wide variety of server capabilities, Serveez also contains some client functionality. This may be necessary when a server is meant to establish a connection to another server in response to an incoming request. For example, imagine a protocol where a client tells the server, “Let me be the server. Please connect to this host at this port”. You are also able to implement pure clients.
  • platform portability
    When writing this software the authors were always mindful of platform portability. Serveez compiles and runs on various Unix platforms as well as on Windows systems. See Porting issues, for details. Most of the routines in the core library can be used without regard to the platform on which you are programming or the details of its underlying system calls. Exceptions are noted in the documentation. Platform portability also means that the server code you write will run on other systems, too.
  • powerful configuration capabilities
    Server configuration has always been a complicated but very important issue. When Serveez starts up it runs the configuration file using the programming language Guile. In contradiction, other (server) applications just read their configuration files and remember the settings in it. This makes them powerful enough to adapt the Serveez settings dynamically. Using the Guile interpreter also means that you can split your configuration into separate files and load these, perhaps conditionally, from the main configuration file.
  • easy server implementation
    Serveez is a server framework. When implementing a new server the programmer need pay little or no attention to the networking code but is free to direct his attention to the protocol the server is meant to support. That protocol may be an established one such as HTTP, or may be a custom protocol fitting the specific application’s requirements. The Writing servers section describes this process in detail.
  • code reusability
    The Serveez package comes along with a core library (depending on the system this is a static library, shared library or a DLL) and its API which contains most of the functionality necessary to write an Internet server. Most probably, a programmer can also use the library for other (network programming related) purposes.
  • server instantiation and network port sharing
    Once you have written a protocol server and integrated into Serveez’s concept of servers the user can instantiate (multiply) the server. At the first glimpse this sounds silly, but with different server configurations it does not. If, for example, an administrator wishes to run multiple HTTP servers with different document roots, Serveez will handle them all in a single process. Also if the same administrator wants to run a HTTP server and some other server on the same network port this is possible with Serveez. You can run a single server on different network ports, too.

2.2 I/O Strategy

Serveez’s I/O strategy is the traditional select method. It is serving many clients in a single server thread. This is done by setting all network handles to non-blocking mode. We then use select to tell which network handles have data waiting. This is the traditional Unix style multiplexing.

An important bottleneck in this method is that a read or sendfile from disk blocks if the data is not in core at the moment. Setting non-blocking mode on a disk file handle has no effect. The same thing applies to memory-mapped disk files. The first time a server needs disk I/O, its process blocks, all clients have to wait, and raw non-threaded performance may go to waste.

Unfortunately, select is limited to the number of FD_SETSIZE handles. This limit is compiled into the standard library, user programs and sometimes the kernel. Nevertheless, Serveez is able to serve about one thousand and more clients on GNU/Linux, a hundred on Win95 and more on later Windows systems.

We chose this method anyway because it seems to be the most portable.

An alternative method to multiplex client network connections is poll. It is automatically used when ‘configure’ finds poll to be available. This will work around the builtin (g)libc’s select file descriptor limit.

2.2.1 Limits on open filehandles

Any Unix

The limits set by ulimit or setrlimit.


See the Solaris FAQ, question 3.45.


Use sysctl -w kern.maxfiles=nnnn to raise limit.


See Bodo Bauer’s /proc documentation. On current 2.2.x kernels,

echo 32768 > /proc/sys/fs/file-max

increases the system limit on open files, and

ulimit -n 32768

increases the current process’ limit. We verified that a process on Linux kernel 2.2.5 (plus patches) can open at least 31000 file descriptors this way. It has also been verified that a process on 2.2.12 can open at least 90000 file descriptors this way (with appropriate limits). The upper bound seems to be available memory.

Windows 9x/ME

On Win9x machines, there is quite a low limit imposed by the kernel: 100 connections system wide (!). You can increase this limit by editing the registry key HKLM\System\CurrentControlSet\Services\VxD\MSTCP\MaxConnections. On Windows 95, the key is a DWORD; on Windows 98, it’s a string. We have seen some reports of instability when this value is increased to more than a few times its default value.

Windows NT/2000

More than 2000 connections tested. It seems like the limit is due to available physical memory.

2.3 Alternatives to Serveez’s I/O strategy

One of the problems with the traditional select method with non-blocking file descriptors occurs when passing a large number of descriptors to the select system call. The server loop then goes through all the descriptors, decides which has pending data, then reads and handles this data. For a large number of connections (say, 90000) this results in temporary CPU load peaks even if there is no network traffic.

Along with this behaviour comes the problem of “starving” connections. Connections which reside at the beginning of the select set are processed immediately while those at the end are processed significantly later and may possibly die because of buffer overruns. This is the reason why Serveez features priority connection: it serves listening sockets first and rolls the order of the remaining connections. In this way, non-priority connections are handled in a “round robin” fashion.

Other server implementations solve these problems differently. Some start a new process for each connection (fully-threaded server) or split the select set into pieces and let different processes handle them (threaded server). This method shifts the priority scheduling to the underlying operating system. Another method is the use of asynchronous I/O based upon signals where the server process receives a signal when data arrives for a connection. The signal handler queues these events in order of arrival and the main server loop continuously processes this queue.

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3 Server

3.1 Introduction to servers

Serveez is a kind of server server. It allows different protocol servers to listen on various TCP/UDP ports, on ICMP sockets and on named pipes. Servers are instantiated with a certain configuration. It is possible to run multiple different servers on the same port.

This chapter covers all questions about how to write your own Internet protocol server with this package. Most of the common tasks of such a server have got a generic solution (default routines) which could be “overridden” by your own routines. There are some examples within this package. They are showing the possibilities with this package and how to implement servers.

The ‘foo’ server does not do anything at all and is of no actual use but could be a basis for a new protocol server. We are now going to describe how this specific server works. Eventually the reader might get an impression of what is going on.

For better understanding the text below we will use the following terminology:

server definition

A server definition is a svz_servertype_t structure which contains server specific members like its name, different callbacks, a single default configuration and a list of configuration items which determines what can be configured.

server configuration

A server configuration can be any kind of structure. The default server configuration must be specified within the server definition (see above). When instantiating a server (which is done via the configuration file) the configuration items specified in the server definition get processed and are put into a copy of the default configuration. Thus we get an instance.

server instance

A server instance is a copy of the server definition including the modified server configuration. A server gets instantiated by the configuration file parser. The concept of server instances has been introduced because we wanted Serveez to have the following features. A single server can have multiple instances with different behaviour due to different server configurations. A server instance can be bound to multiple port configurations. Different server instances (of the same and/or different server type) can share the same port configuration.

port configuration

A port configuration in Serveez is represented by the svz_portcfg_t structure. Depending on a shared flag it contains different type of information specifying a transport endpoint. See Define ports, for more on this topic. It also can be a special configuration item within a server configuration. This is necessary if a server needs for some reason a remote transport endpoint. A server instance does not usually need to know about the port configuration it is bound to.

3.2 Writing servers

Serveez is meant to be a server framework. That is why it supports various ways to implement Internet servers. First of all there are some servers already included in the main serveez package (see Existing servers). These are called ‘Builtin servers’. Another possibility to add a new server are ‘Embedded servers’ which are shared libraries (or DLL’s) containing the server implementation. These can be dynamically loaded by Serveez at runtime. This kind of server is also called ‘Server modules’. A third possibility are the ‘Guile servers’ which allow even unexperienced schemers to write an Internet server.

This section describes each of the above possibilities in detail.

3.2.1 Embedded servers

The core library of Serveez can be used to write standalone server modules. Serveez defines a certain interface for shared libraries which contain such server modules. If Serveez detects an unknown server type (server type which is not builtin) in its configuration file it tries to load a shared library containing this server type during startup. Prerequisites

In order to implement a server module you need an existing installation of Serveez. This can be achieved issuing the following commands:

$ ./configure --enable-shared --prefix=/usr/local
$ make
$ make install

After successful installation you are able to compile and link against the Serveez core API. The headers should be available in /usr/local/include and the library itself ( or libserveez.dll) is located in /usr/local/lib if you passed the configure script ‘--prefix=/usr/local’. Server definition

The interface mentioned in the introduction is defined via the extern declaration of the server type in the shared library of the server module. Imagine you want to implement a server type called ‘foo’. This requires the external symbol foo_server_definition in the shared library. You can achieve this inserting the following lines into your header file:

/* Either Unices.  */
extern svz_servertype_t foo_server_definition;

/* Or Windows.  */
__declspec (dllexport) extern svz_servertype_t foo_server_definition;

The data symbol foo_server_definition must be statically filled with the proper content (See Builtin servers.)

3.2.2 Guile servers

This section describes the Guile interface to Serveez which provides the ability to write servers with Guile. Of course, you could do this without any help from Serveez, but it makes the task a lot easier. This interface reduces the Guile implementation of an Internet server to a simple data processor. Underlying libserveez

Scheme Procedure: libserveez-features

Return a list of symbols representing the features of the underlying libserveez. For details, See Library features. Special Data Types

Serveez extends Guile by various new data types which represent internal data structures of Serveez’s core API.

  • #<svz-servertype> represents a server type.
  • #<svz-server> represents a server (an instance of a server type).
  • #<svz-socket> represents a socket structure. Passing Binary Data

The new binary data type (#<svz-binary>) provides access to any kind of unstructured data. It manages the data exchange between Guile and Serveez. There are some conversion procedures for strings and lists which help to process this binary data in a more complex (guile’ish) way.

Scheme Procedure: binary->string binary

Convert the given binary smob binary into a string. Return the string itself.

Scheme Procedure: string->binary string

Convert the given string into a binary smob. The data pointer of the binary smob is marked as garbage which must be free’d in the sweep phase of the garbage collector.

Scheme Procedure: binary? obj

Return #t if obj is an instance of the binary smob type.

Scheme Procedure: list->binary list

Convert the scheme list list into a binary smob. Each of the elements of list is checked for validity. The elements can be either exact numbers in a byte’s range or characters.

Scheme Procedure: binary->list binary

Convert the given binary smob binary into a scheme list. The list is empty if the size of binary is zero.

Scheme Procedure: binary-search binary needle

Search through the binary smob binary for needle, which can be an exact number, character, string or another binary smob. Return #f if the needle could not be found, or a positive number indicating the position of the first occurrence of needle in the binary smob binary.

Scheme Procedure: binary-set! binary index value

Set the byte at position index of the binary smob binary to the value given in value which can be either a character or an exact number.

Scheme Procedure: binary-ref binary index

Obtain the byte at position index of the binary smob binary.

Scheme Procedure: binary-length binary

Return the size in bytes of the binary smob binary.

Scheme Procedure: binary-concat! binary append

Append either the binary smob or string append onto the binary smob binary. If binary has been a simple data pointer reference it is then a standalone binary smob as returned by string->binary.

Scheme Procedure: binary-subset binary start [end]

Create a subset binary smob from the given binary smob binary. The range of this subset is specified by start and end both inclusive (thus the resulting size is end - start + 1). With a single exception: If end is not given or specified with -1, return all data until the end of binary.

Scheme Procedure: binary-reverse binary

Return a new binary smob with the reverse byte order of the given binary smob binary.

Scheme Procedure: binary-reverse! binary

Perform an in-place reversal of the given binary smob binary and return it.

Scheme Procedure: binary-long-ref binary index

Return the long value of the binary smob binary at the array index index.

Scheme Procedure: binary-long-set! binary index value

Set the long value of the binary smob binary at the array index index to the given value value. Return the previous (overridden) value.

Scheme Procedure: binary-int-ref binary index

Return the int value of the binary smob binary at the array index index.

Scheme Procedure: binary-int-set! binary index value

Set the int value of the binary smob binary at the array index index to the given value value. Return the previous (overridden) value.

Scheme Procedure: binary-short-ref binary index

Return the short value of the binary smob binary at the array index index.

Scheme Procedure: binary-short-set! binary index value

Set the short value of the binary smob binary at the array index index to the given value value. Return the previous (overridden) value.

Scheme Procedure: binary-char-ref binary index

Return the char value of the binary smob binary at the array index index.

Scheme Procedure: binary-char-set! binary index value

Set the char value of the binary smob binary at the array index index to the given value value. Return the previous (overridden) value. Server Definition

In order to set up a new server type, you use the procedure define-servertype!. This procedure takes one argument which must be an associative list specifying the server type in detail. There are optional and mandatory elements you can set up in this alist.

The following example shows the overall syntax of this procedure:

(define-servertype! '(

  ;; Mandatory: server type prefix for later use in (define-server!)
  (prefix          . "foo")

  ;; Mandatory: server type description
  (description     . "guile foo server")

  ;; Mandatory for TCP and PIPE servers: protocol detection
  (detect-proto    . foo-detect-proto)

  ;; Optional: global server type initialisation
  (global-init     . foo-global-init)

  ;; Optional: server instance initialisation
  (init            . foo-init)

  ;; Optional: server instance finalisation
  (finalize        . foo-finalize)

  ;; Optional: global server type finalisation
  (global-finalize . foo-global-finalize)

  ;; Mandatory for TCP and PIPE servers: socket connection
  (connect-socket  . foo-connect-socket)

  ;; Optional: server instance info
  (info-server     . foo-info-server)

  ;; Optional: client info
  (info-client     . foo-info-client)

  ;; Optional: server instance reset callback
  (reset           . foo-reset)

  ;; Optional: server instance notifier
  (notify          . foo-notify)

  ;; Mandatory for UDP and ICMP servers: packet handler
  (handle-request  . foo-handle-request)

  ;; Mandatory: server type configuration (may be an empty list)
  (configuration   . (

    ;; The server configuration is an alist (associative list) again.
    ;; Each item consists of an item name and a list describing the
    ;; item itself.
    ;; Syntax: (key . (type defaultable default))
    (foo-integer       . (integer  #t 0))
    (foo-integer-array . (intarray #t (1 2 3 4 5)))
    (foo-string        . (string   #t "default-foo-string"))
    (foo-string-array  . (strarray #t ("guile" "foo" "server")))
    (foo-hash          . (hash     #t (("foo" . "bar"))))
    (foo-port          . (portcfg  #t foo-port))
    (foo-boolean       . (boolean  #t #t))
Scheme Procedure: define-servertype! args

Define a new server type based on args. (If everything works fine you have a freshly registered server type afterwards.) Return #t on success. Predefined Procedures

The following subset of procedures may be used to implement a Guile server. They should be used within the callbacks defined in the define-servertype! procedure. Each of these callbacks gets passed the appropriate arguments needed to stuff into the following procedures. Please have a look at the example Guile servers for the details.

Scheme Procedure: svz:sock? sock

Return #t if the given cell sock is an instance of a valid #<svz-socket>, otherwise #f.

Scheme Procedure: svz:sock:check-request sock [proc]

Set the check-request member of the socket structure sock to proc. Return the previously handler if there is any.

Scheme Procedure: svz:sock:check-oob-request sock [proc]

Set the check-oob-request callback of the given socket structure sock to proc, returning the previous callback (if there was any set before). The callback is run whenever urgent data (out-of-band) has been detected on the socket.

Scheme Procedure: svz:sock:send-oob sock oob

Send byte oob as urgent (out-of-band) data through the underlying TCP stream of TCP sock. Return #t on successful completion and otherwise (either it failed to send the byte or the passed socket is not a TCP socket) #f.

Scheme Procedure: svz:sock:handle-request sock [proc]

Set the handle-request member of the socket structure sock to proc. Return the previously set handler if there is any.

Scheme Procedure: svz:sock:boundary sock boundary

Setup the packet boundary of the socket sock. The given string value boundary can contain any kind of data. If boundary is an exact number, set up the socket to parse fixed sized packets. More precisely, set the check-request callback of the given socket structure sock to an internal routine which runs the socket’s handle-request callback when it detects a complete packet specified by boundary.

For instance, you can arrange for Serveez to pass the handle-request procedure lines of text by calling (svz:sock:boundary sock "\n").

Scheme Procedure: svz:sock:floodprotect sock [flag]

Set or unset the flood protection bit of the given socket sock. Return the previous value of this bit (#t or #f). The flag argument must be either boolean or an exact number and is optional.

Scheme Procedure: svz:sock:print sock buffer

Write buffer (string or binary smob) to the socket sock. Return #t on success and #f on failure.

Scheme Procedure: svz:sock:final-print sock

Schedule the socket sock for shutdown after all data within the send buffer queue has been sent. You should call this right before the last call to svz:sock:print.

Scheme Procedure: svz:sock:no-delay sock [enable]

Turn the Nagle algorithm for the TCP socket sock on or off depending on the optional enable argument. Return the previous state of this flag (#f if Nagle is active, #t otherwise). By default this flag is switched off. This socket option is useful when dealing with small packet transfer in order to disable unnecessary delays.

Scheme Procedure: svz:sock:send-buffer sock

Return the send buffer of the socket sock as a binary smob.

Scheme Procedure: svz:sock:send-buffer-size sock [size]

Return the current send buffer size and fill status in bytes of the socket sock as a pair of exact numbers. If the optional argument size is given, set the send buffer to the specified size in bytes.

Scheme Procedure: svz:sock:receive-buffer sock

Return the receive buffer of the socket sock as a binary smob.

Scheme Procedure: svz:sock:receive-buffer-size sock [size]

Return the current receive buffers size and fill status in bytes of the socket sock as a pair of exact numbers. If the optional argument size is given, set the receive buffer to the specified size in bytes.

Scheme Procedure: svz:sock:receive-buffer-reduce sock [length]

Dequeue length bytes from the receive buffer of the socket sock, or all bytes if length is omitted. Return the number of bytes actually shuffled away.

Scheme Procedure: svz:sock:connect host proto [port]

Establish a network connection to the given host [ :port ]. If proto equals PROTO_ICMP the port argument is ignored. Valid identifiers for proto are PROTO_TCP, PROTO_UDP and PROTO_ICMP. The host argument must be either a string in dotted decimal form, a valid hostname or an exact number in host byte order. When giving a hostname this operation might block. The port argument must be an exact number in the range from 0 to 65535, also in host byte order. Return a valid #<svz-socket> or #f on failure.

Scheme Procedure: svz:sock:disconnected sock [proc]

Set the disconnected-socket member of the socket structure sock to proc. The given callback runs whenever the socket is lost for some external reason. Return the previously set handler if there is one.

Scheme Procedure: svz:sock:kicked sock [proc]

Set the kicked-socket callback of the given socket structure sock to proc and return any previously set procedure. This callback gets called whenever the socket gets closed by Serveez intentionally.

Scheme Procedure: svz:sock:trigger sock [proc]

Set the trigger callback of the socket structure sock to proc and return any previously set procedure. The callback is run when the trigger-condition callback returns #t.

Scheme Procedure: svz:sock:trigger-condition sock [proc]

Set the trigger-condition callback for the socket structure sock to proc. Return the previously set procedure if available. The callback is run once every server loop indicating whether the trigger callback should be run or not.

Scheme Procedure: svz:sock:idle sock [proc]

Set the idle callback of the socket structure sock to proc. Return any previously set procedure. The callback is run by the periodic task scheduler when the idle-counter of the socket structure drops to zero. If this counter is not zero it gets decremented once a second. The idle callback can reset idle-counter to some value and thus can re-schedule itself for a later task.

Scheme Procedure: svz:sock:idle-counter sock [counter]

Return the socket structure sock’s current idle-counter value. If the optional argument counter is given, the set the idle-counter. Please have a look at the svz:sock:idle procedure for the exact meaning of this value.

Scheme Procedure: svz:sock:parent sock [parent]

Return the given socket’s sock parent and optionally set it to the socket parent. Return either a valid #<svz-socket> object or an empty list.

Scheme Procedure: svz:sock:referrer sock [referrer]

Return the given socket’s sock referrer and optionally set it to the socket referrer. Return either a valid #<svz-socket> or an empty list.

Scheme Procedure: svz:sock:server sock [server]

Return the #<svz-server> object associated with the given argument sock. The optional argument server can be used to redefine this association and must be a valid #<svz-server> object. For a usual socket callback like connect-socket or handle-request, the association is already in place. But for sockets created by svz:sock:connect, you can use it in order to make the returned socket object part of a server.

Scheme Procedure: svz:sock:local-address sock [address]

Return the current local address as a pair like (host . port) with both entries in network byte order. If you pass the optional argument address, you can set the local address of the socket sock.

Scheme Procedure: svz:sock:remote-address sock [address]

Return the current remote address as a pair like (host . port) with both entries in network byte order. If you pass the optional argument address, you can set the remote address of the socket sock.

Scheme Procedure: svz:sock:find ident

Return the #<svz-socket> specified by ident, a pair of integers in the form (identification . version). If that socket no longer exists, return #f.

Scheme Procedure: svz:sock:ident sock

Return a pair of numbers identifying the given #<svz-socket> sock, which can be passed to svz:sock:find. This may be necessary when you are passing a #<svz-socket> through coserver callback arguments in order to verify that the passed #<svz-socket> is still valid when the coserver callback runs.

Scheme Procedure: svz:sock:protocol sock

Return one of the PROTO_TCP, PROTO_UDP, PROTO_ICMP, PROTO_RAW or PROTO_PIPE constants indicating the type of the socket structure sock. If there is no protocol information available, return #f.

Scheme Procedure: svz:read-file port size

Return either a binary smob containing a data block read from the open input port port with a maximum number of size bytes, or the end-of-file object if the underlying ports end has been reached. The size of the returned binary smob may be less than the requested size size if it exceed the current size of the given port port. Throw an exception if an error occurred while reading from the port.

Scheme Procedure: svz:server? server

Return #t if the given cell server is an instance of a valid #<svz-server>, otherwise #f.

Scheme Procedure: svz:server:listeners server

Return a list of listening #<svz-socket> smobs to which the given server instance server is currently bound, or an empty list if there is no such binding yet.

Scheme Procedure: svz:server:clients server

Return a list of #<svz-socket> client smobs associated with the given server instance server in arbitrary order, or an empty list if there is no such client.

Scheme Procedure: svz:server:config-ref server key

Return the configuration item specified by key of the given server instance server. You can pass this procedure a socket, too, in which case the appropriate server instance is looked up. If the given string key is invalid (not defined in the configuration alist in define-servertype!), then return an empty list.

Scheme Procedure: serveez-port? name

Return #t if the given string name corresponds with a registered port configuration, otherwise #f.

Scheme Procedure: serveez-server? name

Check whether the given string name corresponds with an instantiated server name and return #t if so.

Scheme Procedure: serveez-servertype? name

Check whether the given string name is a valid server type prefix known in Serveez and return #t if so. Otherwise return #f.

Scheme Procedure: serveez-exceptions [enable]

Control the use of exception handlers for the Guile procedure calls of Guile server callbacks. If the optional argument enable is #t, enable exception handling; if #f, disable it. Return the current (boolean) setting.

Scheme Procedure: serveez-nuke [exit-value]

Shutdown all network connections and terminate after the next event loop. You should use this instead of calling quit. Optional arg exit-value specifies an exit value for the serveez program. It is mapped to a number via scm_exit_value.

Scheme Procedure: serveez-loadpath [args]

Make the search path for the Serveez core library accessible to Scheme. Return a list a each path as previously defined. If args is specified, override the current definition of this load path with it. The load path is used to tell Serveez where it can find additional server modules.

Scheme Procedure: serveez-interfaces [args]

Make the list of local interfaces accessible to Scheme. Return the local interfaces as a list of ip addresses in dotted decimal form. If args are specified, they are added as additional local interfaces.

Scheme Procedure: getrpc [arg]

Lookup a network rpc service arg (name or service number), and return a network rpc service object. If given no arguments, it behave like getrpcent.

Scheme Procedure: setrpc [stayopen]

Open and rewind the file /etc/rpc. If the stayopen flag is non-zero, the net data base will not be closed after each call to getrpc. If stayopen is omitted, this is equivalent to calling endrpcent. Otherwise it is equivalent to calling setrpcent with arg 1.

Scheme Procedure: portmap prognum versnum [protocol [port]]

Establish a (portmap service) mapping between the triple [prognum,versnum,protocol] and port on the machine’s portmap service. The value of protocol is most likely IPPROTO_UDP or IPPROTO_TCP. If instead protocol and port are omitted, destroy all mapping between the triple [prognum,versnum,*] and ports on the machine’s portmap service.

Scheme Procedure: portmap-list [address]

Return a list of the current RPC program-to-port mappings on the host located at IP address address, which defaults to the local machine’s IP address. Return an empty list if either there is no such list available or an error occurred while fetching the list.

Scheme Procedure: svz:coserver:dns host callback

Enqueue the host string argument into the internal DNS coserver queue. When the coserver responds, the procedure callback is run as (callback addr). The addr argument passed to the callback is a string representing the appropriate IP address for the given hostname host.

Scheme Procedure: svz:coserver:reverse-dns addr callback

Enqueue the given addr argument, which must be an IP address in network byte order, into the internal reverse DNS coserver queue. When the coserver responds, the procedure callback is run as (callback host) where host is the hostname of the requested IP address addr.

Scheme Procedure: svz:coserver:ident sock callback

Enqueue the given #<svz-socket> sock into the internal ident coserver queue. When the coserver responds, it runs the procedure callback as (callback user), where user is the corresponding username for the client connection sock. Callback Prototypes

The Guile interface of Serveez is completely callback driven. Callbacks can be set up in the associative list passed to define-servertype!, or by using the predefined procedures described in the previous section. Each of the callbacks is passed certain arguments and is meant to return specific values to indicate success or failure. This section describes each of these callbacks.

Scheme Procedure: global-init servertype

This callback is invoked once for every type of server right after the define-servertype! statement. Here you can initialise resources shared between all instances of your server type. The callback is optional and can be set up in define-servertype!. It should return zero to indicate success and non-zero to indicate failure. If the global initialiser fails, Serveez will refuse to register the server type.

Scheme Procedure: global-finalize servertype

If you want to free shared resources, which were possibly allocated within the global initialiser, you can do so here. The callback is invoked when Serveez shuts down (issued by serveez-nuke) or the server type gets unregistered for some reason. It should return zero to signal success. The callback can be set up in define-servertype! and is optional.

Scheme Procedure: init server

Within this callback you can initialise everything you might need for a single instance of your server. The callback is invoked for each server instance which has been created by define-server! and should return zero to indicate success, otherwise Serveez rejects the server instance. The callback can be set up in define-servertype! and is optional.

Scheme Procedure: finalize server

The server instance finaliser gets its instance representation passed as argument. You need to free all resources used by this server instance which might have been allocated within the server instance initialiser or consumed while running. You can set this callback in the define-servertype! statement. The callback is optional and should return zero to indicate success.

Scheme Procedure: detect-proto server socket

Connection oriented protocols like TCP and PIPE allow more than one server to be listening on the same network port. Therefore, it is necessary to be able to detect the type of client connecting to a port.

This callback takes two arguments; the first is the server instance and the second is the client socket object containing the client connection information. You can set up this callback in the define-servertype! statement.

Serveez may invoke this callback several times as data becomes available from the client until one of the servers recognises it. The servers can retrieve the data received so far using the svz:sock:receive-buffer call.

To indicate successful client detection, you need to return a non-zero value. (Note that for historical reasons, this is inconsistent with other procedures which return zero on successful completion.) Once the server has indicated success, Serveez invokes any further callbacks for the connection only on that server.

If no server has recognised the client after the first 16 bytes, Serveez will close the connection. The connection will also be closed if the client has not sent enough data for a server to recognise it within 30 seconds of connecting.

If multiple servers are listening on the same network port, Serveez invokes this callback for each of them in an arbitrary order. Only one server at most should indicate successful detection.

This callback is mandatory for servers which get bound to connection oriented protocol (TCP and PIPE) port configurations by bind-server!.

Scheme Procedure: connect-socket server socket

If the client detection signalled success, this callback is invoked to assign the client connection to a server instance. The arguments are the same as the detection callback. In this callback you can assign all the connection specific callbacks for your server and perform some initial tasks. Basically you should specify the handle-request and/or check-request callback. This can be achieved by calling svz:sock:handle-request and svz:sock:check-request. The connect-socket callback is also mandatory for connection oriented protocols and must be defined in define-servertype!. On success you should return zero, otherwise the connection will be shutdown by Serveez.

Scheme Procedure: info-server server

This callback gets invoked when requested by the builtin Control Protocol Server. The callback is optional and can be set up in define-servertype!. The returned character string can be multiple lines separated by \r\n (but without a trailing separator). Usually you will return information about the server instance configuration and/or state.

Scheme Procedure: info-client server socket

This callback is optional. You can set it up in the define-servertype! procedure. It is meant to provide socket structure specific information. (The socket structure is a client/child of the given server instance.) You need to return a single line character string without trailing newlines. The information provided can be requested by the builtin Control Protocol Server.

Scheme Procedure: notify server

The server instance notifier callback will be invoked whenever there is idle time available. In practice, it is run approximately once a second. A server instance can use it to perform periodic tasks. The callback is optional and can be set up in define-servertype!.

Scheme Procedure: reset server

This callback is invoked when the Serveez process receives a SIGHUP signal which can be issued via ‘killall -HUP serveez’ from user land. If the underlying operating system does not provide SIGHUP there is no use for this callback. It provides the possibility to perform asynchronous tasks scheduled from outside Serveez. You can optionally set it up in the define-servertype! procedure.

Scheme Procedure: handle-request socket binary size

This callback is invoked whenever a complete packet has been detected in the receive buffer. The packet data is passed to the callback as a #<svz-binary>. The size argument is passed for convenience and specifies the length of the packet in bytes.

The detection, and therefore the invocation, can be made in one of two ways. When Serveez can determine itself when a packet is complete, the callback will be invoked directly. Serveez can make this determination for connections with packet oriented protocols such as UDP and ICMP, or if you tell Serveez how to parse the packet using svz:sock:boundary sock delimiter or svz:sock:boundary sock size and do not specify a check-request callback.

Whenever you specify a check-request callback to determine when a packet is complete, it becomes the responsiblity of that callback to invoke handle-request itself.

Serveez recognises two different return value meanings. For connection oriented protocols (TCP and PIPE), zero indicates success and non-zero failure; on failure, Serveez will shutdown the connection. For packet oriented protocols (UDP and ICMP), a non-zero return value indicates that your server was able to process the passed packet data, otherwise (zero return value) the packet can be passed to other servers listening on the same port configuration.

This callback must be specified in define-servertype! for packet oriented protocols (UDP and ICMP) but is optional otherwise. You can modify the callback by calling svz:sock:handle-request.

Scheme Procedure: check-request socket

This callback is invoked whenever new data has arrived in the receive buffer. The receive buffer of the given #<svz-socket> can be obtained using svz:sock:receive-buffer. The callback is initially not set and can be set up with svz:sock:check-request. Its purpose is to check whether a complete request was received. If so, it should be handled (by running the handle-request callback) and removed from the receive buffer (using svz:sock:receive-buffer-reduce). The callback is for connection oriented protocols (TCP and PIPE) only. You should return zero to indicate success and non-zero to indicate failure. On failure Serveez shuts the connection down.

Scheme Procedure: disconnected socket

The disconnected callback gets invoked whenever the socket is lost for some external reason and is going to be shutdown by Serveez. It can be set up with svz:sock:disconnected.

Scheme Procedure: kicked socket reason

This callback gets invoked whenever the socket gets closed by Serveez intentionally. It can be set up with svz:sock:kicked. The reason argument can be either KICK_FLOOD, indicating the socket is a victim of the builtin flood protection, or KICK_QUEUE which indicates a send buffer overflow.

Scheme Procedure: idle socket

The idle callback gets invoked from the periodic task scheduler, which maintains a idle-counter for each socket structure. This counter is decremented whenever Serveez becomes idle and the callback is invoked when it drops to zero. The idle callback can set its socket’s idle-counter to some value with the procedure svz:sock:idle-counter and thus re-schedule itself for a later task. You can set up this callback with svz:sock:idle.

Scheme Procedure: trigger-condition socket

This callback is invoked once every server loop for the socket structure. If you return #f nothing else is happening. Otherwise the trigger callback will be invoked immediately. You can set up the callback using the procedure svz:sock:trigger-condition.

Scheme Procedure: trigger socket

The trigger callback is invoked when the trigger-condition returns #t. The callback can be set up with the procedure svz:sock:trigger. Returning a non-zero value shuts the connection down. A zero return value indicates success. This callback can be used to perform connection related updates, e.g., you can ensure a certain send buffer fill.

Scheme Procedure: check-oob-request socket oob-byte

This callback is invoked whenever urgent data (out-of-band) has been detected on a socket. Initially this event is ignored and the callback can be set up with the procedure svz:sock:check-oob-request. The oob-byte argument is a number containing the received out-of-band data byte ranging from 0 to 255. If the callback returns non-zero the connection will be shutdown. A zero return value indicates success. You can use svz:sock:send-oob to send a single out-of-band data byte.

Please note: The urgent data is not supported by all operating systems. Also it does not work for all types of network protocols. We verified it to be working for TCP streams on GNU/Linux 2.x.x and Windows 95; let us know if/how it works on other platforms.

3.2.3 Builtin servers

All of the servers listed in Existing servers are builtin servers. The following sections describe in detail how to setup a new builtin server type. This kind of server will be part of the Serveez executable. That is why you should make it configurable in the configure script via a ‘--enable-xxxserver’ argument. Making and configuring preparations

Serveez is configured and built via automake and autoconf. That is why you are not supposed to write your own Makefiles but simplified Makefile.ams. Automake will automatically generate dependencies and compiler/linker command lines. Here are the steps you basically need to follow:

  • Change to the src/ directory in the source tree.
  • Edit the Add your sub directory name and library name which you are going to create.
  • Now create the sub directory and change into it.
  • You need to create a new therein. If you want to have this file configured you need to add a further line to the AC_OUTPUT statement in which is in the top level directory. You have to put at least the following into the newly created
    noinst_LIBRARIES = libfoo.a
    libfoo_a_SOURCES = foo-proto.h foo-proto.c
    INCLUDES = $(SERVEEZ_CFLAGS) -I$(top_srcdir)/src
  • Just have a look at all the other server directories. For more information about automake read the info pages. Server header file foo-proto.h

This file contains at least your server’s extern declaration of your server definition which must be available from the outside. The foo server implements all kinds of configuration items which can be integers, integer arrays, strings, string arrays, port configurations, booleans and hash maps. Every item of the server configuration can later be manipulated from the configuration file. Server implementation file foo-proto.c

If you want to define default values for your configuration you have to define them somewhere and put them into the default configuration structure. This structure will be used to instantiate your server. For this example we simply called it simply foo_config.

In order to associate the configuration items in a server configuration to keywords within the configuration file you have to define an array of key-value-pairs. This is done in the foo_config_prototype field. There are several macros which make different associations. These are the SVZ_REGISTER_* macros which take three arguments. The first argument is the keyword which will occur in the configuration file, the second is the associated item in your default configuration structure and the last argument specifies if this item is defaultable or not. Server definition

The server definition is in a way the ‘class’ of your server. Together with the default values (foo_config_prototype) it serves as a template for newly instantiated servers. The structure contains a long and a short description of your server. The short name is used as the prefix for all server instances of this specific type. The long description is used in the control protocol (See Control Protocol Server.). The server definition also contains the callbacks your server (mandatorily) provides. Server callbacks

There are several callback routines, which get called in order to instantiate the server and for describing the actual behaviour of your server. Here are the description of all of these callbacks. Some of them have to be implemented. Others have reasonable default values.

global initializer (optional)

This callback is executed once for every type of server. Here you can initialize data or whatever is shared between all instances of your server. For instance the HTTP server initializes its file cache here.

global finalizer (optional)

If you want to free shared resources which were possibly allocated within the global initializer you can do so here. The foo server frees its default hash previously allocated in the global initializer.

instance initializer (mandatory)

Within this routine you can initialize everything you might need for one instance of your server. The foo server does not do anything in this callback.

instance finalizer (optional)

The server instance finalizer gets its instance representation as argument. You have to free all resources used by this server instance.

protocol detection (mandatory)

Because it is possible to have more than one server listening on one network port we need to detect the type of client which is connecting to this port. The foo server checks if the first five bytes the client was sending is identifying it as a foo client. This routine is getting two arguments where the first one is a pointer to this servers instance and the second is the client socket object containing all information of the client connection. This structure is described a bit later. Be patient. For successful client detection return non-zero value.

socket connection (mandatory)

If the client detection signaled success this routine is called to assign the client connection to the server instance. The arguments are just the same as in the detection routine. In this callback you can assign all the connection specific callbacks for your server and do some initial things. The foo server sets the check_request callback to the default svz_sock_check_request which is using the packet delimiter information to find whole packets. When a client sent such a packet the handle_request callback is executed. That is why the foo server assigns the handle_request method.

client info (optional)

If this callback is given the control protocol (See Control Protocol Server.) can give information about a specific client if requested with ‘stat id NUM’. The first argument given is the server instance and the second one the client’s socket structure. You have to return a static single line character string.

server info (optional)

This function is called when listing the server instances via ‘stat all’ from the control protocol (See Control Protocol Server.). The returned character string might be multilined separated by \r\n (no trailing separator). Usually you will return all the server configuration information.

notifier (optional)

If this callback is not NULL it is called whenever there is some time left. It gets the server instance itself as argument. Actually it gets called every second.

handle request (mandatory for UDP and ICMP servers)

The arguments to this callback are the client’s socket structure, the address of the packet data and its length. When implementing a UDP or ICMP server you need to return non-zero if your server could process the packet. Thus it is possible that there are multiple UDP servers on a single port. Make your server available

You distribute your server by editing the cfgfile.c file in the src/ directory. There you have to include the servers header file and add the server definition by calling svz_servertype_add More detailed description of the callback system and structures

The client connection information is stored within the svz_socket_t object. All of the client connection specific callbacks get this object as first argument. Following is a description of the most important elements of this object.

int id

The socket id is a unique id for a client connection.

int version

This item validates this socket structure. If you pass the id and version to a coserver you can check if the delivered socket structure is the original or not within the coserver callback.

int proto

The proto flag determines a server sockets protocol type which can be PROTO_PIPE, PROTO_TCP, PROTO_UDP, PROTO_ICMP or PROTO_RAW.

int flags

The flag field of the client connection contains informations about the state of this connection. See socket.h in the src/libserveez/ directory for more information. Basically this bitfield specifies how this object is handled by the main server loop.

int userflags

This bitfield could be used for protocol specific information. You can use it for any information.

char *boundary, int boundary_size

If you are going to write a packet oriented protocol server you can use the svz_sock_check_request method to parse packets. These two properties describe the packet delimiter.

char *send_buffer, int send_buffer_size, int send_buffer_fill

This is the outgoing data for a client connection object.

char *recv_buffer, int recv_buffer_size, int recv_buffer_fill

Within the receive buffer all incoming data for a connection object is stored. This buffer is at least used for the client detection callback.

int read_socket (svz_socket_t)

This callback gets called whenever data is available on the socket. Normally, this is set to a default function which reads all available data from the socket and feeds it to check_request, but specific sockets may need other policies.

int write_socket (svz_socket_t)

This routine is called when data is is valid in the output buffer and the socket gets available for writing. You normally leave this callback untouched. It simply writes as much data as possible to the socket and removes the data from the send buffer.

int disconnected_socket (svz_socket_t)

This gets called whenever the socket is lost for some external reason.

int connected_socket (svz_socket_t)

If some piece of code tries to connect to another host via svz_tcp_connect this connection might be established some time later. This callback gets called when the socket is finally connected.

int kicked_socket (svz_socket_t, int)

We call this whenever the socket gets closed by us. The second argument specifies a reason.

int check_request (svz_socket_t)

This gets called whenever data was read from the socket. Its purpose is to check whether a complete request was read, and if it was, it should be handled and removed from the input buffer.

int handle_request (svz_socket_t, char *, int)

This gets called when the check_request got a valid packet. The request arguments contains the actual packet and the second argument is the length of this packet including the packet delimiter.

int idle_func (svz_socket_t)

This callback gets called from the periodic task scheduler. Whenever idle_counter (see below) is non-zero, it is decremented and idle_func gets called when it drops to zero. idle_func can reset idle_counter to some value and thus can re-schedule itself for a later task.

int idle_counter

Counter for calls to idle_func.

void *data

Miscellaneous field. Listener keeps array of server instances here. This array is NULL terminated. Some servers store server specific information here.

void *cfg

When the final protocol detection has been done cfg should contain a pointer to the actual configuration hash map taken from the server instance object. Using coservers

Coservers are designed to complete blocking tasks. Each coserver runs in its own thread/process. There are several coservers implemented: the dns, reverse dns and ident coserver. You need to implement the callback which gets called when a coserver completed its task. This routine must be a svz_coserver_handle_result_t. The first argument is the actual coserver result which might be NULL if the request could not be fulfilled and the latter two arguments are the arguments you specified yourself when issuing the request. To invoke a coserver you use one of the svz_coserver_* macros. The foo server uses the reverse dns coserver to identify the host name of the remote client.

Next: , Previous: , Up: Server   [Contents][Index]

3.3 Some words about server configuration

If you define a server you basically pass an instance name and a list of items to the define-server! procedure. Each item has a name and a value. A value has a type. We provide several types: integers (numbers), integer arrays, strings, string arrays, booleans (yes/no-values), hashes (associations) and port configurations.

The following table shows how each kind of value is set up in the configuration file. item is the name of the item to be configured.


Example: (item . 42)

Integer array

Example: (item . (0 1 2 3))


Example: (item . "a character string")

String array

Example: (item . ("abc" "cba" "bca" "acb"))


A normal boolean in guile is represented by #t or #f. But the configuration file parser additional understand some bare words and numbers.
Example: (item . #f)


Hash maps associate keys with values. Both must be character strings.
Example: (item . (key1 . "value1") (key2 . "value2"))

Port configuration

See Define ports, for more information on this. When configuring a port configuration you need to define it via define-port! previously and put its symbolic name into the configuration.
Example: (item . foo-tcp-port)

The next chapter describes the servers currently implemented using Serveez. The configuration items used by each of them are described in the following format:

NameOfTheItem (Type, default: DefaultValue, Comments)

Description of the configuration item named ‘NameOfTheItem’ (case sensitive). ‘Type’ can be either ‘integer’, ‘integer array’, ‘string’, ‘string array’, ‘boolean’, ‘hash’ or ‘port configuration’. The ‘Comments’ is an optional text.

The example configuration file data/serveez.cfg contains an example definition of each server already implemented. You can copy and modify the example for an easy start.

3.4 Existing servers

3.4.1 HTTP Server General description

The integrated HTTP server was originally meant to be a simple but fast document server. But now it can even execute CGI scripts. The GET, HEAD and POST methods are fully functional. Additionally Serveez produces directory listings when no standard document file (e.g., index.html) has been found at the requested document node (directory). Furthermore it implements a file cache for speeding up repetitive HTTP request.

In comparison to other web server projects like Apache and Roxen this web server is really fast. Comparative benchmarks will follow. The benchmark system is a 233 MHz Mobile Pentium MMX. Both the server and the client (http_load - multiprocessing http test client) ran on the same computer.

Small files

The small-file test load consists of 1000 files, each 1KB long, requested randomly.

concurrent fetches   1   10   50  100  200  500  1000
hits/second        501  520  481  475  420  390   295

The CGI test load consists of a trivial “hello world” C program. I noticed GNU/Linux (2.2.17 in this case, probably others too) to throw “Resource temporarily unavailable” errors when forking very fast. This limits the test to about 200 concurrent fetches on the test system.

Large files

The large-file test load consists of 100 files, each 1MB long, requested randomly. Also, each connection is throttled to simulate a 33.6Kbps modem. Note that 1000 33.6Kbps connections is 3/4 of a T3. There was no problem to get 1000+ concurrent fetches. Configuration

The following options can be set from the configuration file.

indexfile (string, default: index.html)

The indexfile parameter is the default file served by the HTTP server when the user does not specify a file but a document node (e.g.,

docs (string, default: ../show)

The docs parameter is the document root where the server finds its web documents.

userdir (string, default: public_html)

Each ‘~user’ request gets converted into the given users home directory. The string will be appended to this directory. Its default value is ‘public_html’.

cgi-url (string, default: /cgi-bin)

This parameter is the first part of the URL the HTTP server identifies a CGI request. For instance if you specify here /cgi-bin and the user requests then the HTTP server tries to execute the program within the cgi-dir (see below) and pipes its output to the user.

cgi-dir (string, default: ./cgibin)

The cgi-dir is the CGI document root (on the server).

cgi-application (hash, default: empty)

Within the MinGW32 port you can use this hash to associate certain file suffices with applications on your computer (e.g., pl with perl). This is necessary because there is no possibility to check whether a file is executable on Win32.

cache-size (integer, default: 200 kb)

This specifies the size of the document cache in bytes for each cache entry.

cache-entries (integer, default: 64)

This parameter specifies the maximum number of HTTP file cache entries (files). When you instantiate more than one HTTP server the biggest value wins. The HTTP file cache is shared by all HTTP servers.
Please note: If your harddrive/filesystem combination proves to be faster than the HTTP file cache you should disable it by setting both cache-size and cache-entries to zero.

timeout (integer, default: 15)

The timeout value is the amount of time in seconds after which a keep-alive connection (this is a HTTP/1.1 feature) will be closed when it has been idle.

keepalive (integer, default: 10)

On one keep-alive connection can be served the number of keepalive documents at all. Then the connection will be closed. Both this and the timeout value are just to be on the safe side. They protect against idle and high traffic connections.

default-type (string, default: text/plain)

The default-type is the default content type the HTTP server assumes if it can not identify a served file by the types hash and the type-file (see below).

type-file (string, default: /etc/mime.types)

This should be a file like the /etc/mime.types on Unix systems. It associates file suffices with MIME types.

types (hash, default: empty)

If you want to specify special content types do it here. This parameter is a hash map associating file suffices with HTTP content types (MIME types).

admin (string, default: root@localhost)

Your address, where problems with the server should be e-mailed. This address appears on some server-generated pages, such as error documents.

host (string, default: localhost)

This is the host name of your web server. Sometimes the server has to send back its own name to the client. It will use this value. Be aware that you cannot invent such a name.

nslookup (boolean, default: false)

If this is true the HTTP server invokes a reverse DNS lookup for each client connection in order to replace the remote ip address with the remote host name in the access logfile.

ident (boolean, default: false)

If this is true the HTTP server processes identd requests for each client connection for logging purposes.

logfile (string, default: http-access.log)

The location of the access logfile. For each HTTP request a line gets appended to this file.

logformat (string, default: CLF)

The format of the access logfile. There are special placeholders for different kinds of logging information. The default log format is the Common Log Format (CLF). It contains a separate line for each request. A line is composed of several tokens separated by spaces.

CLF = host ident authuser date request status bytes

If a token does not have a value then it is represented by a hyphen (-). The meanings and values of these tokens are as follows:

%h (host)

The fully-qualified domain name of the client, or its IP number if the name is not available.

%i (ident)

This is the identity information reported by the client. Not active, so we will see a hyphen (-).

%u (authuser)

If the request was for an password protected document, then this is the userid used in the request.

%t (date)

The date and time of the request, in the following format:

date   = [day/month/year:hour:minute:second zone]
day    = 2*digit
month  = 3*letter
year   = 4*digit
hour   = 2*digit
minute = 2*digit
second = 2*digit
zone   = (`+' | `-') 4*digit
%R (request)

The request line from the client, enclosed in double quotes (").

%r (referrer)

Which document referred to this document.

%a (agent)

What kind of web browser did the remote client use.

%c (status)

The three digit status code returned to the client.

%l (bytes)

The number of bytes in the object returned to the client, not including any headers.

3.4.2 IRC Server General description

Internet Relay Chat. The mother of all chat systems. The integrated IRC server is intended to be compatible with the EFNet. There are no good possibilities to test this in real life, so it is still under heavy construction. But it can be used as a standalone server anyway.

IRC itself is a teleconferencing system, which (through the use of the client-server model) is well-suited for running on many machines in a distributed fashion. A typical setup involves a single process (the server) forming a central point for clients (or other servers) to connect to, performing the required message delivery/multiplexing and other functions.

The server forms the backbone of IRC, providing a point for clients and servers to connect to. Clients connect to talk to each other. Servers connect to build up a network of servers. IRC server connections have to build up a spanning tree. Loops are not allowed. Each server acts as a central node for the rest of the network it sees. Configuration

The following table shows the configuration keys provided. Most of the configuration items are similar to those of an Hybrid IRC server. They seem archaic at first sight but IRC operators are used to it. Refer to the Hybrid documentation for further information. It can be found on the EFNet web page.

MOTD-file (string, default: ../data/irc-MOTD.txt)

When a user initially joins it will get this file’s content as the message of the day comment. When changing on disk the server will notice that and reload the file automatically.

INFO-file (string, default: no file)

The INFO-files content gets displayed when the user issues the /INFO command.

tsdelta (integer, default: 0)

This value is the timestamp delta value to UTC (Coordinated Universal Time) in seconds.

channels-per-user (integer, default: 10)

Configures the maximum number of channels a single local user can join.

admininfo (string, no default)

Some administrative information delivered on the /ADMIN command.

M-line (string, no default, mandatory)

The TCP level configuration of this IRC server. The server info field is sometimes given to the client for informational use. The server will croak about if the settings do not correspond with the actual bindings. The format of this line is:

":" virtual hostname
":" optional bind address (real hostname)
":" server info: "World's best IRC server"
":" port
A-line (string, no default, mandatory)

The administrative info, printed by the /ADMIN command.

":" administrative info (department, university)
":" the server's geographical location
":" email address for a person responsible for the IRC server
Y-lines (string array, no default, suggested)

The connection classes. They are used in other parameters (e.g., I-lines). A Y-line describes a group of connections. You usually have at least two Y-lines: One for server connections and one for client connections. Format of each line is:

":" class number (higher numbers refer to a higher priority)
":" ping frequency (in seconds)
":" connect frequency in seconds for servers, 0 for
    client classes
":" maximum number of links in this class
":" send queue size
I-lines (string array, no default, mandatory)

Authorization of clients, wildcards permitted, a valid client is matched user@ip OR user@host.

":" user@ip, you can specify ‘NOMATCH’ here to force
    matching user@host
":" password (optional)
":" user@host
":" password (optional)
":" connection class number (YLine)
O-lines (string array, no default, optional)

Authorize operator, wildcards allowed.

":" user@host, user@ forces checking ident
":" password
":" nick
o-lines (string array, no default, optional)

Authorize local operator.

":" user@host, user@ forces checking ident
":" password
":" nick
C-lines (string array, no default, networked)

List of servers to connect to. Note: C and N lines can also use the user@ combination in order to check specific users (ident) starting servers. C and N lines are usually given in pairs.

":" host name
":" password
":" server name (virtual)
":" port (if not given we will not connect)
":" connection class number (YLine)
N-lines (string array, no default, networked)

Servers which may connect.

":" host name
":" password
":" server name (virtual host name)
":" password
":" how many components of your own server's name to strip
    off the front and be replaced with a ‘*’.
":" connection class number (YLine)
K-lines (string array, no default, optional)

Kill user, wildcards allowed.

":" host
":" time of day
":" user

Next: , Previous: , Up: Existing servers   [Contents][Index]

3.4.3 Control Protocol Server

If the GNU Serveez package is configured with the control protocol enabled, running ‘serveez --help’ will show the option -P and the following documentation applies. Otherwise, feel free to skip to the next section. General description

Serveez implements something like a telnet protocol for administrative purposes. You just need to start a telnet session like:

$ telnet 42420

After pressing RET you will be asked for a password which you might setup passing Serveez the -P argument. See Using Serveez. The next section describes the interactive commands available. Using the Control Protocol


This command will give you a very short help screen of all available commands.


This command closes the connection to Serveez.

restart ident

Restarts the internal ident coserver. This is useful if you just want to start a new one if the old one died or is otherwise unusable.

restart dns

Restarts the internal dns lookup server.

restart reverse dns

Restarts the internal reverse dns lookup server.


This might be useful if Serveez seems to be unstable but you do not want to restart it. With ‘killall’ you disconnect all client network connections except the control protocol connections.

kill id NUM

Disconnects a specific connection identified by its ID. These IDs will be stated when you type ‘stat con’ (see below).


General statistics about Serveez. This will show you some useful information about the computer Serveez is running on and about the state of Serveez in general.

stat coserver

Statistics about all running coserver instances.


This command is for selecting certain server instances to be listed. SERVER is one of server names you specified in the configuration file.

stat id NUM

Show statistics about a specific connection. This will give you all available information about every connection you specified. See Writing servers, for more information about how to provide these information.

stat con

Connection statistics. This will give a list of all socket structures within Serveez. If you want more detailed information about specific connections, coservers or servers you need to request these information with ‘stat id NUM’ or ‘stat all’.

stat all

Server and coserver instance statistics. This command lists all the information about instantiated servers and coservers. See Writing servers, for more information about how to provide these information.

stat cache

HTTP cache statistics. This command produces an output something like the following where ‘File’ is the short name of the cache entry, ‘Size’ the cache size, ‘Usage’ the amount of connections currently using this entry, ‘Hits’ the amount of cache hits, ‘Recent’ the cache strategy flag (newer entries have larger numbers) and ‘Ready’ is the current state of the cache entry.

File                      Size  Usage  Hits Recent Ready  45393      0     0      1 Yes
texinfo.tex             200531      0     0      2 Yes
shayne.txt                2534      0     1      1 Yes

Total : 248458 byte in 3 cache entries
kill cache

Reinitialize the HTTP file cache. Flushes all files from the cache. Configuration

There is nothing to be configured yet.

3.4.4 Foo Server General description

The Foo Server is a simple example on how to write Internet protocol servers with Serveez. See Writing servers. Configuration

There are all kinds of configuration items. They are used to explain the implementation of servers. A complete list will follow.

port (port configuration, default: tcp, 42421, *)

Sets up the TCP port and local address.

bar (integer, no default)

Some integer value. Printed as server information.

reply (string, default: Default reply)

Some string. Printed as server information.

messages (string array, default: ...)

Some string array which is actually a list of strings. Also printed as server information.

ports (integer array, default: 1, 2, 3, 4)

Some array of integer numbers. Printed as server information.

assoc (hash, default, default: ...)

An hash map associating keys with values. Printed as server information.

truth (boolean, default: true)

Some boolean value. Printed as server information.

3.4.5 SNTP Server General

The SNTP server can be queried with the ‘netdate’ command. It is used to synchronize time and dates between Internet hosts. The protocol is described in the ARPA Internet RFC 868. Thus it is not really an SNTP server as described by RFC 2030 (Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI). It is rather an excellent example on how to implement a UDP server in Serveez.

This protocol provides a site-independent, machine readable date and time. The Time service sends back time in seconds since midnight on January first 1900.

One motivation arises from the fact that not all systems have a date/time clock, and all are subject to occasional human or machine error. The use of time-servers makes it possible to quickly confirm or correct a system’s idea of the time, by making a brief poll of several independent sites on the network. Configuration

The configuration of this server does not require any item.

3.4.6 Gnutella Spider What is it ?

The Gnutella net is a peer-to-peer network which is based on client programs only. There are no servers. The network itself is formed by client connections only. Generally the Gnutella network is for sharing files of any kind.

This Gnutella spider is for seeking the needle in the haystack. Once connected to the network it regularly tries to find certain files in there. It keeps track of all connected clients and tries to reconnect them if the current connections are lost.

Gnutella, however has nothing to do with the GNU project. The original client is just a free (as in free beer) piece of software. With Serveez you have a free (as in freedom) way to use it. Have a look at the Gnutella page for further information. Configuration

The Gnutella spider knows the following configurations items.

net-url (string, default: gnutella-net)

If you want to see the host catcher list of this Gnutella spider you can connect to this port with any WWW browser at http://host:port/net-url. The host:port combinations depend on the bindings.

hosts (string array, no default)

This is the start of the haystack, the initial host list of the clients the spider tries to connect to. Each list item should be of the format ip:port (e.g., ‘’). You can also pass Internet host names. If the port information is left blank it defaults to 6346. If you need some entry point for the Gnutella network have a look at or

search (string array, default: Puppe3000, Meret Becker)

This is the needle. Each search line is either a set of space delimited tokens where every token must match. Or a kind of wildcard expression including ‘?’ and ‘*’. Search lines are always matched case insensitive.

search-limit (integer, default: 30)

This limits how many results the Gnutella spider returns to other people searching your files. This is for protection against * search requests.

max-ttl (integer, default: 5)

Every Gnutella packet has got a TTL. This is the maximum TTL allowed for outgoing packets. When a packet comes in it gets its TTL value decremented and is forwarded to it destination. If however an incoming packet has a TTL larger than max-ttl the ttl value is set to max-ttl. This is necessary since most people use far too large TTL values.

ttl (integer, default: 5)

When creating a new Gnutella packet we use this as TTL. Please use a sane value. This ttl needs not to be as large as it is for IP packets. A value below 10 is more than enough. Have a look at the Gnutella page for a calculation of a ’sane value’.

download-path (string, default: /tmp)

This is where the spider saves needles in.

share-path (string, default: /tmp)

Here are all the files we share with others. The Gnutella spider will recurse into directories. So be careful with this option.

max-downloads (integer, default: 4)

Maximum number of concurrent downloads from the network.

max-uploads (integer, default: 4)

Maximum number of concurrent uploads to the network.

connection-speed (integer, default: 28)

This is what we send as our connection speed in KBit/s. We also use this value to throttle down the network transfer rate for file uploads.

min-speed (integer, default: 28)

Search for needles on hosts with a minimum speed. Set it to 0 if you do not care about that. This value is in KBit/s, too.

file-extensions (string array, default: empty list)

If we get replies on search queries we check if the file extension of this reply matches one of these extensions. Useful extensions are ‘mp3’ and ‘mpg’.

connections (integer, default: 4)

This is the number of concurrent connections the Gnutella spider tries to keep up to the network. The IP addresses and the port information is taken from the host catcher hash.

force-ip (string, default: not set)

You can force the Gnutella spider to send outgoing replies with this IP as host information. Must be in dotted decimals notation. This is useful if you are behind a masquerading gateway. You need to install some kind of port forwarder on the gateway so other people can reach you from the outside. Serveez is a good port forwarder.

force-port (integer, default: not set)

Force the Gnutella spider to send outgoing replies with the force-port as port information. See above for more information.

disable (boolean, default: false)

With this configuration option you can disable the bindings for a Gnutella server instance. This means that no remote client can connect without being told so (e.g., by push requests).

3.4.7 Tunnel Server General description

The Tunnel server is for mapping one port configuration to another. So we should rather speak of a port forwarder. Two port forwarders can form a tunnel. Generally this means that you can setup Serveez to accept network or pipe connections in order to pass all transfer data on this line to another port configuration. This can be useful to work around gateways and firewalls. When instantiating an ICMP source or destination you must ensure root privileges for the application. On Windows NT and Windows 2000 you need to be either logged in as Administrator or have set the registry key HKLM\System\CurrentControlSet\Services\Afd\Parameters\DisableRawSecurity to 1 (DWORD). One of the given examples in serveez.cfg shows how you can setup a tunnel server for forwarding a pipe connection. Please keep in mind when forwarding a TCP or pipe connection over ICMP or UDP you loose reliability since the latter two are packet oriented rather than connection oriented. We are not willing to implement our own TCP stack to work on ICMP/UDP directly.

Forwarding between the same types of connection is always possible. When forwarding to an ICMP tunnel we use a special protocol which we will outline in the following section. Extended ICMP protocol specification

Since ICMP (Internet Control Message Protocol) does have a fixed packet format we had to extend it in order to use it for our own purposes. The protocol field of the IP header contains a binary ‘1’ which is the identifier for ICMP (e.g., ‘6’ identifies TCP). When creating an ICMP socket the IP header is always generated by the kernel. This is the main difference to raw sockets where the IP header must be generated at userspace level.

When receiving an ICMP packet it also contains the IP header. When sending an ICMP packet you must not prepend this IP header. The kernel will do this itself. The IP header always follows the actual ICMP header followed by the ICMP packet data. Since this section does not cover raw sockets we leave the IP header structure out here.

The modified ICMP message format is as:

01Message type.
11Message type sub code.
42Senders unique identifier.
62Sequence number.
82Port number.
100 - 65506Packet load.

Each of these fields can be modified and processed by Serveez and do not get touched by the kernel at all. The ICMP socket implementation of Serveez differentiates two types of sockets: listening and connected ICMP sockets. This is non-standard because it actually makes no sense since there is no difference for the kernel. The introduction of these semantics allow Serveez to forward data between connection-oriented (TCP and named pipes) and packet-oriented (UDP and ICMP) protocols.

Message type

Valid message types are for instance ‘8’ for an echo message and ‘0’ for its echo reply. These two messages are used for the systems builtin ping services. Serveez uses its own message type identifier which is ‘42’ (ICMP_SERVEEZ) by default.

Message type sub code

Serveez also defines its own message type sub codes described in the following table.

Sub codeConstant identifierDescription
0ICMP_SERVEEZ_DATApacket contains data
3ICMP_SERVEEZ_CLOSEdisconnection message
4ICMP_SERVEEZ_CONNECTconnect message

The checksum field of the ICMP header is used to check the ICMP headers and the payloads (packet data) validity. We are using the standard Internet Checksum algorithm described in RFC 1071. If the check failed we drop the packet.

Senders unique identifier

The senders identifier field is used to determine if a received packet has been sent by the sender itself and should therefore be dropped. This happens because each ICMP socket setup for receiving gets all sent ICMP packets system wide. Thus Serveez will even be notified if the kernel creates some echo reply or destination unreachable message due to a request completely outside the scope of Serveez.

Sequence number

Each connected ICMP socket increments its sequence number when sending a packet. Thus a connection message type packet of such a socket always has a zero sequence number. This field could (but is not yet) also be used to reorder ICMP packets or to detect missing packets.

Port number

The port field of the modified packet format helps Serveez to establish connected ICMP sockets. A simple packet filter detects if a received packet is kind of reply to a sockets sent packets by comparing this port number. The packet is dropped if the comparison fails and it is not a listening socket.

Except the data message type subcode all ICMP packets created and sent by Serveez have a zero payload. The connect message subcode identifies a new connection and the disconnection message subcode its shutdown without actually transmitting data. These two subcodes emulate a TCP connections connect, accept and shutdown system call. Configuration

This might be the most easiest configuration to setup. You essentially need to define the source port configuration and the target port configuration. The serveez.cfg in the data/ directory shows two example configurations how to tunnel TCP connections over UDP and ICMP. The UDP tunnel accesses the standard HTTP port 80 and the ICMP tunnel accesses the standard Telnet port 23.

source (port configuration, no default)

The source port configuration. This is usually the same you bind the server to.

target (port configuration, no default)

The target port configuration.

3.4.8 Fake Ident Server General description

Most systems run the ’ident protocol’ on port 113. Internet hosts can connect to that port and find out what user is having a connection to the host. For example a webserver can query your username when you fetch a file (e.g., Serveez’ internal ident-coserver can do that). Most IRC servers protect themselves by allowing only users that have a valid ident response. Therefore mIRC (for windoze) has a built in ident server. This fake ident server can be used to ’fake’ a response. This is useful when you connect through a masquerading gateway and the gateway cannot handle ident requests correctly. (Or, of course, you are using windoze, need an ident response and do not have mIRC at hand.)

This server has two modes of operation. In one mode all requests get ‘ERROR : NO-USER’ as response. This is a valid but not very helpful response. The other mode makes the server send a valid and useful response. It contains a system type and a username. The system type is usually ’UNIX’. Others are valid but never used (at least i have never seen something else). Configuration

This server is easy to configure.

systemtype (string, default: UNIX)

The system type to respond. The username field of the response has other meanings depending on this field, so do not make things up here. Read the RFC to learn more.

username (string, default: <NULL>)

If no username is set (which means this field does not appear in the configuration file) the server runs in the flag-all-requests-as-error mode. Use your favourite nickname here.

3.4.9 Passthrough Server General description

The program passthrough server provides basic inetd functionality. Basically it can accept connections and pass this connection to the standard input (stdin) and standard output (stdout) handles of programs. Depending on the platform (operating system) the user is able to configure different methods how this can be achieved. Configuration

This server has different types of configuration options specifying its behaviour. Some of them are mandatory and some are optional. The very least to configure is the program to be started when a new connection is made.

binary (string, no default)

This parameter specifies the program to execute when a new connection has been accepted. The parameter is mandatory and must be a fully qualified file name (including path).

directory (string, no default)

This will be the working directory of the executed program. If you omit this parameter the server uses the current directory (the directory is not changed).

user (string, no default)

If you omit this parameter no user or group will be set for the started program. Otherwise you need to specify this information in the format ‘user[.group]’. If the group is omitted the user’s primary group will be used.

argv (string array, no default)

This list of character strings is going to be the program’s argument list (command line). If the first list item (which is argv[0] and the program’s name) is left blank it defaults to the name specified in the binary parameter.

do-fork (boolean, default: true)

This flag specifies the method used to pass the connection to the program. If it is true the server uses the Unix’ish fork and exec method. Otherwise it will pass the data through a unnamed pair of sockets [ or two pairs of anonymous pipes ].

single-threaded (boolean, default: true)

This parameter applies to servers bound to UDP and ICMP port configurations only. For programs which process all incoming packets and eventually time out, the program is said to be ‘single-threaded’ and should use a true value here. If a program gets a packet and can receive further packets, it is said to be a ‘multi-threaded’ program, and should use a false value.

thread-frequency (integer, default: 40)

The optional thread-frequency parameter specifies the maximum number of program instances that may be spawned from the server within an interval of 60 seconds.

3.4.10 Mandel Server

[ Example Mandelbrot picture. ]
Mandelbrot Set General description

The distributed Mandelbrot server is an Internet server completely written in Guile with the help of the API provided by the underlying Serveez application. The reader will not see any occurrence of the networking API of Guile.

It implements a protocol called ‘dnc’. ‘dnc’ - short for “Distributed Number Cruncher”. The Mandelbrot server manages the computation of a graphic visualization of the Mandelbrot set fractal. Each client can connect to the server and ask for something to calculate and is meant to send its result back to the server. Finally the server produces a bitmap in the XPM format and uses a specified viewer application to bring it onto your screen. Configuration

The server can be setup to manage the calculation of the Mandelbrot set at various locations (rectangular region in the complex plane), in a specific pixel resolution and colour depth. Moreover you can define the name of the final output file and the viewer application the output file is displayed with.

start (string, default: -2.0-1.5i)

Specifies the upper left corner of the final bitmap in the complex plane.

end (string, default: +1.1+1.5i)

Specifies the lower right corner of the final bitmap in the complex plane.

x-res (integer, default: 320)

The real part pixel resolution.

y-res (integer, default: 240)

The imaginary part pixel resolution.

colors (integer, default: 256)

Number of maximum colours used in the bitmap. Also determines the maximum iteration depth.

outfile (string, default: mandel.xpm)

When the Mandel server has managed to calculate the whole bitmap it produces an output file in the XPM format. You can specify the name and location of this output file.

viewer (string, default: xv)

Here you can setup your favourite bitmap viewer application. It should be able to parse and display the XPM format.

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4 Coserver

4.1 What are coservers

If it is necessary to complete blocking tasks in Serveez you have to use coservers. The actual implementation differs on platforms. On Unices they are implemented as processes communicating with Serveez over pipes. On Win32 Serveez uses threads and shared memory.

4.2 Writing coservers

4.2.1 Making and configuring preparations

First you have to change into the src/libserveez/coserver/ directory of the Serveez package. Then edit the and add your header and implementation file to the libcoserver_la_SOURCES variable.

4.2.2 Coserver header file

You have to declare the coserver handle routine here. This callback gets the input buffer argument and delivers the output buffer result. Both of these buffers are supposed to be lines separated by a ‘\n’.

4.2.3 Coserver implementation file

Here you need to #include "libserveez/coserver/coserver.h" and implement the coserver handle routine declared in the coserver header file. This can be any blocking system call. On successful completion you can return the result or NULL on errors. The input and output buffers are plain strings and can have any format with one exception. Because the coservers communicate via a line protocol with Serveez these buffers must not contain ‘\n’ (0x0d).

4.2.4 Make your coserver available in Serveez

For this you have to edit coserver.h and coserver.c files which are located in the src/libserveez/coserver/ directory. In the header file you have to define a further COSERVER_* id (macro) and set the MAX_COSERVER_TYPES define to the appropriate value. Then you should define a further svz_coserver_* macro in the same file.

In coserver.c you have to implement the svz_coserver_* macro. This macro takes three arguments. The first is always specific to your coserver and is used to create the actual request string. Then follows the result callback routine, and an optional argument for this callback. The latter two are simply passed to the svz_coserver_send_request routine. This routine takes four arguments where the first is the previously defined COSERVER_* id and the second is the input buffer for the coserver handle routine without the trailing ‘\n’.

Then you need to add your coserver to the svz_coservertypes array specifying the COSERVER_* id, the coserver description, the coserver handle routine discussed above, the number of coserver instances to be created and an optional initialization routine.

Previous: , Up: Coserver   [Contents][Index]

4.3 Existing coservers

4.3.1 Identification (Ident) coserver

The Identification protocol is briefly documented in RFC1413. It provides a means to determine the identity of a user of a particular TCP connection. Given a TCP port number pair, it returns a character string which identifies the owner of that connection on the server’s (that is the client’s) system.

This is a connection based application on TCP. A server listens for TCP connections on TCP port 113 (decimal). Once a connection is established, the server reads a line of data which specifies the connection of interest. If it exists, the system dependent user identifier of the connection of interest is sent as the reply. The server may then either shut down the connection or it may continue to read/respond to more queries.

The Ident coserver is a client to this kind of service. For every established network connection you can use this service by calling the appropriate macro from coserver.h. But you could also use the Ident coserver as is without this macro. The messages from Serveez to this coserver are formatted this way:

RemoteAddressInDottedDecimals ":" RemotePort ":" LocalPort

svz_coserver_ident (sock, MyIdentCallback, sock->id, sock->version);

In this context sock is of type svz_socket_t and MyIdentCallback is something like the following example. Both of the last two (optional) arguments identify a valid socket structure and user can be NULL if there is no ident daemon running on the foreign machine. The last two argument within the above macro will be the last two arguments in the callback below. Thus you will know what kind of data the invocation of the callback is related to.

MyIdentCallback (char *user, int id, int version)
  printf ("Identified user: %s\n", user);
  return 0;

4.3.2 Domain Name Server (DNS) coserver

The DNS coserver is using gethostbyname to translate a given hostname to the associated IP address. The format of the coserver input line and the macro from coserver.h is shown below. The IRC server is currently using this coserver for resolving its ‘?-Lines’. See Existing servers, for more information. In the example below realhost is something like ‘’.


svz_coserver_dns (realhost, irc_connect_server, ircserver, NULL);

irc_connect_server (char *ip, irc_server_t *server)
  printf ("The ip address is: %s\n", ip);
  return 0;

4.3.3 Reverse Domain Name Server (reverse DNS) coserver

As easily guessed from the name this coserver is just doing the reverse as the DNS coserver. It translates a given IP address into a hostname using gethostbyaddr. In the macro the ip address is given as an unsigned long in host byte order. The Reverse DNS coserver itself takes something like ‘’.


svz_coserver_reverse (addr, MyReverseCallback, sock->id, sock->version);

MyReverseCallback (char *host, int id, int version)
  printf ("Hostname is: %s\n", host);
  return 0;

Next: , Previous: , Up: GNU Serveez   [Contents][Index]

5 Embedding

This chapter documents how to embed Serveez into C programs and describes all parts of the API it provides.

The Serveez core library provides all of the functionality necessary in order to write Internet protocol servers (currently TCP, UDP, ICMP and RAW sockets), pipe servers (connection-oriented via a pair of named pipes) and coservers in a portable way. All of the included servers are based upon this library, which encapsulates the native network and file system programming interface of different Unices and Windows systems.

The following sections will give the reader an overview about how to use its core library.

5.1 Embedding Serveez

This chapter deals with embedding the Serveez core library into standalone C/C++ applications and using it in order to write additional servers.

5.1.1 Compiling and linking

When you have installed a version of Serveez passing the configure script the $prefix argument, e.g., ‘./configure --prefix=/usr/local’, you will find the libserveez library in /usr/local/lib and the include headers in /usr/local/include. If you want to compile a C program using the Serveez API and link against the Serveez core library libserveez, which is for Unices and libserveez.dll for Windows systems, you need to tell the compiler and linker where to find the headers and libraries.

Most C compilers you can use will understand the following command line options for this purpose. The ‘-I’ argument specifies the directory of additional include headers, the ‘-L’ argument the direcory to additional libraries and the ‘-l’ argument the library itself to link against.

$ cc test.c -I/usr/local/include -o test -L/usr/local/lib -lserveez

In order to obtain the correct compiler and linker flag you can also run the ‘serveez-config’ script which gets installed with the Serveez package. The ‘serveez-config’ script can be invoked with the following set of option.

-h, --help

Displays the usage information.

-v, --version

Displays installed Serveez version.

-l, --ldflags

Prints the linker flags (libraries to link with including directory information).

-c, --cflags

Prints the compiler flags to compile with.

5.1.2 A simple example

The following small example shows how to use the Serveez core library to print the list of known network interface. As you will notice there are three major steps to do: Include the library header with #include <libserveez.h>, initialize the library via svz_boot and finalize it via svz_halt. In between these calls you can use all of the API functions, variables and macros described in Embedding API.

#include <stdio.h>
#include <stdlib.h>
#include <libserveez.h>

static int
display_ifc (const svz_interface_t *ifc,
             void *closure)
  char *addr = svz_inet_ntoa (ifc->ipaddr);

  if (ifc->description)
    /* interface with description */
    printf ("%40s: %s\n",
            ifc->description, addr);
    /* interface with interface # only */
    printf ("%31s%09lu: %s\n",
            "interface # ", ifc->index, addr);
  return 0;

main (int argc, char **argv)
  /* Library initialization.  */
  svz_boot ("example");

  /* Display a list of interfaces.  */
  printf ("local interfaces:\n");
  svz_foreach_interface (display_ifc, NULL);

  /* Library finalization.  */
  svz_halt ();

  return EXIT_SUCCESS;

Previous: , Up: Embedding   [Contents][Index]

5.2 Embedding API

In this chapter the reader will find a short description of each function, global variable and macro provided by the Serveez core library. The API can either be used to implement a new server or coserver module for use with Serveez or for supporting network and server functionality within your own applications without caring about the details and system programming.

Most of the Serveez core library interface functionality should be prefixed with svz_. Small symbols will refer to functions and variables in most cases and big letter symbols refer to macros.

[FIXME: The subsections are named inconsistently because originally, the API reference was a separate document; on merge, weirdness like “Port config funcs” was necessary to avoid conflict with the other “Port configuration” node. —ttn]

5.2.1 Library features

The configure script used to build libserveez takes many options (see Building and installing). Some of these are encapsulated by svz_library_features.

Function: const char * const * svz_library_features (size_t *count)

Return a list (length saved to count) of strings representing the features compiled into libserveez.

Here is a table describing the features in detail:


Present when ‘--enable-debug’.


Present when ‘--enable-heap-count’.


Present when ‘--enable-iflist’.


Present when ‘--enable-poll’ and you have poll(2).


Present when ‘--enable-sendfile’ and you have sendfile(2) or some workalike (e.g., TransmitFile).


Present when svz_log uses a mutex around its internal stdio operations, implying that you have some kind of thread capability (perhaps in a separate library). If your system has fwrite_unlocked, the configure script assumes that fwrite et al already operate in a locked fashion, and disables this.


Present when ‘--enable-flood’.


The networking core. This is always present.

5.2.2 Memory management

The core library of Serveez is able to keep track of the memory an application or part of a program consumes, and also controls itself in the same manner. When you are using this memory allocator interface you can determine and afterwards remove memory leaks. This is a very important feature as servers are by nature long-lived programs.

The three allocator function pointers for malloc, realloc and free make it possible to instruct Serveez to use different kinds of memory, which might be necessary if you want the library to work with shared memory arenas or any other underlying memory API.

Function: void svz_set_mm_funcs (svz_malloc_func_t cus_malloc, svz_realloc_func_t cus_realloc, svz_free_func_t cus_free)

Set the internal memory management functions to cus_malloc, cus_realloc and cus_free, respectively. The default internal values are malloc, realloc and free.

Function: void * svz_malloc (size_t size)

Allocate size bytes of memory and return a pointer to this block.

Function: void * svz_calloc (size_t size)

Allocate size bytes of memory and return a pointer to this block. The memory is cleared (filled with zeros).

Function: void * svz_realloc (void *ptr, size_t size)

Change the size of a block of memory at ptr, previously returned by svz_malloc, to size bytes. If ptr is NULL, allocate a new block.

Function: void svz_free (void *ptr)

Free a block of memory at ptr, previously returned by svz_malloc or svz_realloc. If ptr is NULL, do nothing.

Function: char * svz_strdup (const char *src)

Duplicate the given string src if it is not NULL and has non-zero length. Return the new string.

Function: void svz_get_curalloc (size_t *to)

Write values to to[0] and to[1] representing the number of currently allocated bytes and blocks, respectively. If Serveez was not configured with ‘--enable-debug’, the values are always 0.

5.2.3 Data structures

Since most servers need to store information about its clients or want to keep track of data during runtime, we include a pair of of useful data structures. The actual aim was to provide higher level data structures which the C programming language does not support. Some of the included servers which come with Serveez make extensive use of them. Array

The array data structure is a simple array implementation. Each array has a size and capacity. The array indices range from zero to the array’s size minus one. You can put any kind of data into this array which fits into the size of a pointer. The array grows automatically if necessary.

Function: svz_array_t * svz_array_create (size_t capacity, svz_free_func_t destroy)

Create a new array with the initial capacity capacity and return a pointer to it. If capacity is zero it defaults to some value. If destroy is non-NULL, svz_array_destroy calls that function (typically used to free dynamically allocated memory). For example, if the array contains data allocated by svz_malloc, destroy should be specified as svz_free. If the array contains data which should not be released, destroy should be NULL.

Function: void svz_array_destroy (svz_array_t *array)

Completely destroy the array array. The array handle is invalid afterwards. The routine runs the destroy callback for each element of the array.

Function: void * svz_array_get (svz_array_t *array, size_t index)

Return the array element at the position index of the array array if the index is within the array range. Return NULL if not.

Function: void * svz_array_set (svz_array_t *array, size_t index, void *value)

Replace the array element at the position index of the array array with the value value and return the previous value at this index. Return NULL and do nothing if array is NULL or the index is out of the array range.

Function: void svz_array_add (svz_array_t *array, void *value)

Append the value value at the end of the array array. Do nothing if array is NULL.

Function: void * svz_array_del (svz_array_t *array, size_t index)

Remove the array element at the position index of the array array. Return its previous value or NULL if the index is out of the array’s range.

Function: size_t svz_array_size (svz_array_t *array)

Return the current size of array.

Macro: svz_array_foreach (array, value, i)

Expand into a for-statement header, for iterating over array. On each cycle, value is assigned to successive elements of array, and i the element’s position.

Previous: , Up: Data structures   [Contents][Index] Hashtable

A hashtable associates keys of arbitrary size and content with values. This data structure is also called associative array sometimes because you use keys in order to access values instead of numbers. You cannot store two values associated with the same key. The values can have any simple C types like integers or pointers.

Function: svz_hash_t * svz_hash_create (size_t size, svz_free_func_t destroy)

Create a new hash table with an initial capacity size. Return a non-zero pointer to the newly created hash. The size is calculated down to a binary value. The destroy callback specifies an element destruction callback for use by svz_hash_clear and svz_hash_destroy for each value. If no such operation should be performed the argument must be NULL.

Function: svz_hash_t * svz_hash_configure (svz_hash_t *hash, size_t (* keylen) (const char *) , unsigned long (* code) (const char *) , int (* equals) (const char *, const char *)

Set the internal keylen, code and and equals functions for hash table hash. Return hash.

keylen takes const char *data and returns size_t, the number of bytes in data representing the key.

code takes const char *data and returns unsigned long.

equals takes const char *data1, const char *data2 and returns int, which should be non-zero if equal.

As a special case, a NULL value means don’t set that function, leaving it to its default value.

Function: void svz_hash_destroy (svz_hash_t *hash)

Destroy the existing hash table hash, svz_freeing all keys within the hash, the hash table and the hash itself. If a non-NULL element destruction callback was specified to svz_hash_create, that function is called on each value.

Function: void * svz_hash_delete (svz_hash_t *hash, const char *key)

Delete an existing entry accessed via a key from the hash table hash. Return NULL if there is no such key, otherwise the previous value.

Function: void * svz_hash_put (svz_hash_t *hash, const char *key, void *value)

Add a new element consisting of key and value to hash. When key already exists, replace and return the old value. Note: This is sometimes the source of memory leaks.

Function: void * svz_hash_get (const svz_hash_t *hash, const char *key)

Return the value associated with key in the hash table hash, or NULL if there is no such key.

Function: void svz_hash_foreach (svz_hash_do_t *func, svz_hash_t *hash, void *closure)

Iterate func over each key/value pair in hash. func is called with three void * args: the key, the value and the opaque (to svz_hash_foreach) closure.

Function: size_t svz_hash_size (const svz_hash_t *hash)

Return the number of keys in the hash table hash. If hash is NULL, return zero.

Function: char * svz_hash_contains (const svz_hash_t *hash, void *value)

Return the key associated with value in the hash table hash, or NULL if there is no such value.

Function: int svz_hash_exists (const svz_hash_t *hash, char *key)

Return non-zero if key is stored within the hash table hash, otherwise zero. This function is useful when you cannot tell whether the return value of svz_hash_get (== NULL) indicates a real value in the hash or a non-existing hash key.

5.2.4 svz_address_t

A network address comprises a family, such as AF_INET (also known as IPv4), and its bits in network byte order, such as the bytes 127, 0, 0 and 1 (also known as the IPv4 loopback address). Many libserveez functions take svz_address_t *.

Please note: Although svz_address_t supports1 IPv6, the rest of libserveez it does not (yet). This means you can freely create and manipulate address objects with the functions described in this section, but any attempt to pass to the rest of libserveez an address with a family other than AF_INET will immediately abort the process. When full IPv6 support is in place, this blurb will be deleted and the list returned by svz_library_features will include an appropriate indicator (see Library features).

Function: svz_address_t * svz_address_make (int family, const void *bits)

Return an address object to hold an address in family, represented by bits. family must be one of:


An IPv4 address; bits is in_addr_t *.


(if supported by your system) An IPv6 address; bits is struct in6_addr *.

The bits are expected in network byte order. If there are problems, return NULL.

Function: int svz_address_family (const svz_address_t *addr)

Return the address family of addr.

Function: int svz_address_to (void *dest, const svz_address_t *addr)

Copy the address bits out of addr to dest. Return 0 on success, -1 if either addr or dest is NULL, or the addr family is AF_UNSPEC.

Function: int svz_address_same (const svz_address_t *a, const svz_address_t *b)

Return 1 if a and b represent the same address (identical family and bits), otherwise 0.

Function: const char * svz_pp_address (char *buf, size_t size, const svz_address_t *addr)

Format an external representation of addr into buf, of size bytes. The format depends on the family of addr. For IPv4, this is numbers-and-dots. For IPv6, it is “the most appropriate IPv6 network address format for addr”, according to the manpage of inet_ntop, the function that actually does the work.

If buf or addr is NULL, or size is not big enough, return NULL. Otherwise, return buf.

Function: const char * svz_pp_addr_port (char *buf, size_t size, const svz_address_t *addr, in_port_t port)

Format an external representation of addr and port (in network byte order) into buf, of size bytes. The address xrep (external representation) is done by svz_pp_address, q.v. The rest of the formatting depends on the addr family.

AF_INET (IPv4)xrep:port
AF_INET6 (IPv6)[xrep]:port

If buf or addr is NULL, or size is not big enough, return NULL. Otherwise, return buf.

Function: svz_address_t * svz_address_copy (const svz_address_t *addr)

Return a copy of addr.

Macro: SVZ_SET_ADDR (place, family, bits)

Expand to a series of commands. First, if place is non-NULL, then svz_free it. Next, assign to place a new address object made by calling svz_address_make with family and bits.

Macro: SVZ_PP_ADDR (buf, addr)

Expand to a call to svz_pp_address, passing it buf and sizeof buf, in addition to addr.

Macro: SVZ_PP_ADDR_PORT (buf, addr, port)

Expand to a call to svz_pp_addr_port, passing it buf and sizeof buf, in addition to addr and port.

5.2.5 Utility functions

Within this section you will find some miscellaneous functionality and left overs of the C API.

Function: void svz_log (int level, const char *format, …)

Print a message to the log system. level specifies the prefix.

Function: void svz_log_setfile (FILE *file)

Set the file stream file to the log file all messages are printed to. Can also be stdout or stderr.

Function: int svz_hexdump (FILE *out, char *action, int from, char *buffer, int len, int max)

Dump buffer with the length len to the file stream out. Display description action along with origin and size info first, followed by the hexadecimal text representation. Stop output at either max or len (if max is zero) bytes. from is a numerical identifier of the buffers creator.

Function: char * svz_itoa (unsigned int i)

Convert an unsigned integer to its decimal string representation, returning a pointer to an internal buffer. (You should copy the result.)

Function: unsigned int svz_atoi (char *str)

Convert string str in decimal format to an unsigned integer. Stop conversion on any invalid characters.

Function: char * svz_getcwd (void)

Return the current working directory in a newly allocated string. (You should svz_free it when done.)

Function: int svz_openfiles (int max_sockets)

Check for the current and maximum limit of open files of the current process and try to set the limit to max_sockets.

Function: char * svz_time (long t)

Transform the given binary data t (UTC time) to an ASCII time text representation without any trailing characters.

Function: char * svz_tolower (char *str)

Convert the given string str to lower case text representation.

Function: char * svz_sys_version (void)

Return a statically-allocated string describing some operating system version details.

Function: int svz_socket_unavailable_error_p (void)

Return 1 if there was a "socket unavailable" error recently, 0 otherwise. This checks svz_errno against WSAEWOULDBLOCK (woe32) or EAGAIN (Unix).

Function: const char * svz_sys_strerror (void)

Return a string describing the most recent system error.

The next two functions log (with SVZ_LOG_ERROR) the current system error or network error, forming the prefix of the message using fmt and args. This formatted prefix cannot exceed 255 bytes. The rest of the message comprises: colon, space, error description, newline.

Function: void svz_log_sys_error (char const *fmt, …)

Log the current system error.

Function: void svz_log_net_error (char const *fmt, …)

Log the current network error.

Function: int svz_mingw_at_least_nt4_p (void)

Return 1 if running MinGW (Windows) NT4x or later, otherwise 0.

5.2.6 Networking and other low level functions

This chapter deals with the basic networking and file systems functions. It encapsulates systems calls in a portable manner. These functions should behave identically on Windows and Unices.

Function: char * svz_inet_ntoa (in_addr_t ip)

Convert ip, an address in network byte order, to its dotted decimal representation, returning a pointer to a statically allocated buffer. (You should copy the result.)

Function: int svz_inet_aton (char *str, struct sockaddr_in *addr)

Convert the Internet host address str from the standard numbers-and-dots notation into binary data and store it in the structure that addr points to. Return zero if the address is valid, nonzero otherwise. As a special case, if str is ‘*’ (asterisk), store INADDR_ANY in addr.

Function: int svz_closesocket (svz_t_socket sockfd)

Close the socket sock. Return 0 if successful, -1 otherwise.

Function: int svz_fd_cloexec (int fd)

Set the close-on-exec flag of the given file descriptor fd and return zero on success. Otherwise return non-zero.

Function: int svz_tcp_cork (svz_t_socket fd, int set)

Enable or disable the TCP_CORK socket option of the socket fd. This is useful for performance reasons when using sendfile with any prepending or trailing data not inside the file to transmit. Return zero on success, otherwise non-zero.

Function: int svz_tcp_nodelay (svz_t_socket fd, int set, int *old)

Enable or disable the TCP_NODELAY setting for the socket fd depending on the flag set, effectively enabling or disabling the Nagle algorithm. This means that packets are always sent as soon as possible and no unnecessary delays are introduced. If old is not NULL, save the old setting there. Return zero on success, otherwise non-zero.

Function: int svz_sendfile (int out_fd, int in_fd, off_t *offset, size_t count)

Transmit data between one file descriptor and another where in_fd is the source and out_fd the destination. The offset argument is a pointer to a variable holding the input file pointer position from which reading starts. On return, the offset variable will be set to the offset of the byte following the last byte that was read. count is the number of bytes to copy. Return the number of bytes actually read/written or -1 on errors.

Function: int svz_open (const char *file, int flags, mode_t mode)

Open the filename file and convert it into a file handle. The given flags specify the access mode and the mode argument the permissions if the O_CREAT flag is set.

Function: int svz_close (int fd)

Close the given file handle fd. Return -1 on errors.

Function: int svz_fstat (int fd, struct stat *buf)

Return information about the specified file associated with the file descriptor fd returned by svz_open. Store available information in the stat buffer buf.

Function: FILE * svz_fopen (const char *file, const char *mode)

Open the file whose name is the string pointed to by file and associate a stream with it.

Function: int svz_fclose (FILE *f)

Dissociate the named stream f from its underlying file.

5.2.7 Client connections

Serveez tries to handle all kinds of Internet protocols like TCP (connection oriented), UDP, ICMP and RAW (packet oriented) and communication across named pipes (also connection oriented) in the same way. Therefore it uses a structure called svz_socket_t which is the abstraction of any kind of communication endpoint (can be client or server or both together). TCP sockets

TCP sockets provide a reliable, stream oriented, full duplex connection between two sockets on top of the Internet Protocol (IP). TCP guarantees that the data arrives in order and retransmits lost packets. It generates and checks a per packet checksum to catch transmission errors. TCP does not preserve record boundaries.

Function: svz_socket_t * svz_tcp_connect (svz_address_t *host, in_port_t port)

Create a TCP connection to host host and set the socket descriptor in structure sock to the resulting socket. Return NULL on errors.

Function: int svz_tcp_read_socket (svz_socket_t *sock)

Read all data from sock and call the check_request function for the socket, if set. Return -1 if the socket has died, zero otherwise.

This is the default function for reading from sock.

Function: int svz_tcp_send_oob (svz_socket_t *sock)

If the underlying operating system supports urgent data (out-of-band) in TCP streams, try to send the byte in sock->oob through the socket structure sock as out-of-band data. Return zero on success and -1 otherwise (also if urgent data is not supported). Pipe connections

The pipe implementation supports both named and anonymous pipes. Pipe servers are implemented as listeners on a file system FIFO on Unices or “Named Pipes” on Windows (can be shared over a Windows network).

A FIFO special file is similar to a pipe, except that it is created in a different way. Instead of being an anonymous communications channel, a FIFO special file is entered into the file system.

Once you have created a FIFO special file in this way, any process can open it for reading or writing, in the same way as an ordinary file. However, it has to be open at both ends simultaneously before you can proceed to do any input or output operations on it.

Function: svz_socket_t * svz_pipe_create (svz_t_handle recv_fd, svz_t_handle send_fd)

Create a socket structure containing both the pipe descriptors recv_fd and send_fd. Return NULL on errors.

Function: int svz_pipe_create_pair (svz_t_handle pipe_desc[2])

Create a (non blocking) pair of pipes. This differs in Win32 and Unices. Return a non-zero value on errors.

Function: svz_socket_t * svz_pipe_connect (svz_pipe_t *recv, svz_pipe_t *send)

Create a pipe connection socket structure to the pair of named pipes recv and send. Return NULL on errors.

Function: int svz_invalid_handle_p (svz_t_handle handle)

Return 1 if handle is invalid, otherwise 0.

Function: void svz_invalidate_handle (svz_t_handle *href)

Invalidate the handle pointed at by href.

Function: int svz_closehandle (svz_t_handle handle)

Close handle. Return 0 if successful, -1 otherwise. UDP sockets

The UDP sockets implement a connectionless, unreliable datagram packet service. Packets may be reordered or duplicated before they arrive. UDP generates and checks checksums to catch transmission errors.

Function: svz_socket_t * svz_udp_connect (svz_address_t *host, in_port_t port)

Create a UDP connection to host at port and set the socket descriptor in structure sock to the resulting socket. Return a NULL value on errors.

This function can be used for port bouncing. If you assign the handle_request callback to something server specific and the cfg field of the server’s configuration to the returned socket structure, this socket is able to handle a dedicated UDP connection to some other UDP server.

Function: int svz_udp_write (svz_socket_t *sock, char *buf, int length)

Write buf into the send queue of the UDP socket sock. If length argument supersedes the maximum length for UDP messages it is split into smaller packets. ICMP sockets

The ICMP socket implementation is currently used in the tunnel server which comes with the Serveez package. It implements a user protocol receiving and sending ICMP packets by opening a raw socket with the protocol IPPROTO_ICMP.

The types of ICMP packets passed to the socket can be filtered using the ICMP_FILTER socket option (or by software as done here). ICMP packets are always processed by the kernel too, even when passed to a user socket.

Function: svz_socket_t * svz_icmp_connect (svz_address_t *host, in_port_t port, uint8_t type)

Create an ICMP socket for receiving and sending. Return NULL on errors, otherwise an enqueued socket structure.

Function: int svz_icmp_send_control (svz_socket_t *sock, uint8_t type)

“If you are calling this function we will send an empty ICMP packet signaling that this connection is going down soon.” [ttn sez: huh?]

Function: int svz_icmp_write (svz_socket_t *sock, char *buf, int length)

Send buf with length length via this ICMP socket sock. If length supersedes the maximum ICMP message size the buffer is split into smaller packets. Raw sockets

A raw socket receives or sends the raw datagram not including link-level headers. It is currently used by the ICMP socket implementation of the core library. The IPv4 layer generates an IP header when sending a packet unless the IP_HDRINCL socket option is enabled on the socket. When it is enabled, the packet must contain an IP header. For receiving the IP header is always included in the packet.

Only processes with an effective userid of zero (Administrator or root) or the CAP_NET_RAW capability are allowed to open raw sockets. All packets or errors matching the protocol number specified for the raw socket are passed to this socket. A protocol of IPPROTO_RAW implies enabled IP_HDRINCL and receives all IP protocols. Sending is not allowed.

[FIXME: All funcs internalized! Write something else here!] Passthrough connections

The functions described in this section allow you to pass through client connections to the standard input (stdin) and standard output (stdout) of external programs. Some of the routines deal with the management of program environments. Basically, there are two methods for passing through a duplex connection: the Unix’ish fork and exec method and the shuffle method where the main process keeps control over the communication on the original duplex connection and passes this data through two pairs of pipes, or yet another socket connection, to the child process. All of the three method are implemented calling them SVZ_PROCESS_FORK, SVZ_PROCESS_SHUFFLE_PIPE and SVZ_PROCESS_SHUFFLE_SOCK.

Function: int svz_sock_process (svz_socket_t *sock, char *bin, char *dir, char **argv, svz_envblock_t *envp, int forkp, char *user)

Start a new program bin, a fully qualified executable filename, passing the socket or pipe descriptor(s) in the socket structure sock to its stdin and stdout.

If dir is non-NULL, it specifies the working directory of the new process.

The program arguments and the environment of the new process are taken from argv and envp. Normally argv[0] should be set to the program’s name. If NULL, it defaults to bin.

The forkp argument is a flag that controls the passthrough method. If non-zero, pipe descriptors or the socket descriptor are passed to the child process directly through fork and exec. Otherwise, socket transactions are passed via a pair or pipes or sockets (depending on whether or not the system provides socketpair).

You can pass the user and group identifications in the format ‘user[.group]’ (group is optional), as SVZ_PROCESS_NONE or SVZ_PROCESS_OWNER in the user argument. This specifies the permissions of the new child process. If SVZ_PROCESS_OWNER is passed the permissions are set to the executable file bin owner; SVZ_PROCESS_NONE does not change user or group.

Return the new process id on success, -1 on failure.

Please note: On M$-Windows platforms it is not possible to pass a socket connection to stdin/stdout of a child process. That is why this function creates an inheritable version of the socket and puts the socket handle number into the environment variables SEND_HANDLE and RECV_HANDLE. A spawned child process can use these handles as if they were self-created. After calling WSAStartup the child process can send and recv as usual.

Relatedly, Windoze does not use SIGCHLD to inform the parent when a child dies, so for that platform, you should use the next function (which is not otherwise available):

Function: int svz_mingw_child_dead_p (char *prefix, svz_t_handle *pid)

Check child pointed at by pid by waiting a bit. If it is dead, close and invalidate its handle, and return 1. Otherwise, return 0. prefix is for error messages; it should be either the empty string, or a string ending in colon and space.

On non-Windoze, this is the function you want to use:

Function: int svz_most_recent_dead_child_p (svz_t_handle pid)

Return 1 if a child process pid died recently, updating other internal state by side effect. Otherwise, return 0.

Function: void svz_envblock_setup (void)

Set up internal tables for environment block wrangling.

This function must be called once after svz_boot so that subsequent functions (like svz_envblock_default) can work correctly.

Function: svz_envblock_t * svz_envblock_create (void)

Create and return a fresh environment block, useful for passing to svz_envblock_default and svz_envblock_add. Its size is initially set to zero.

Function: int svz_envblock_default (svz_envblock_t *env)

Fill environment block env with the environment variables from the current process, replacing its current contents (if any).

Function: int svz_envblock_add (svz_envblock_t *env, char *format, …)

Insert a new environment variable into environment block env. The format argument is a printf-style format string describing how to format the optional arguments. You specify environment variables in the ‘VAR=VALUE’ format.

Function: void svz_envblock_destroy (svz_envblock_t *env)

Destroy environment block env completely. Afterwards, env is invalid and should therefore not be further referenced.

Function: void * svz_envblock_get (svz_envblock_t *env)

Convert environment block env into something which can be passed to execve (Unix) or CreateProcess (Windows). Additionally, under Windows, sort the environment block.

(Unfortunately the layout of environment blocks in Unices and Windows differ. On Unices you have a NULL terminated array of character strings (i.e., char **) and on Windows systems you have a simple character string containing the environment variables in the format ‘VAR=VALUE’ each separated by a zero byte (i.e., char *). The end of the list is indicated by a further zero byte.)

5.2.8 Socket management

The functions described in this section deal with the operations on C structures called svz_socket_t. See the description of each function for details on which kind of socket it can handle and what they are for.

Function: int svz_sock_nconnections (void)

Return the number of currently connected sockets.

Function: int svz_sock_write (svz_socket_t *sock, char *buf, int len)

Write len bytes from the memory location pointed to by buf to the output buffer of the socket sock. Also try to flush the buffer to the socket of sock if possible. Return a non-zero value on error, which normally means a buffer overflow.

Function: int svz_sock_printf (svz_socket_t *sock, const char *fmt, …)

Print a formatted string on the socket sock. fmt is the printf-style format string, which describes how to format the optional arguments.

Function: int svz_sock_resize_buffers (svz_socket_t *sock, int send_buf_size, int recv_buf_size)

Resize the send and receive buffers for the socket sock. send_buf_size is the new size for the send buffer, recv_buf_size for the receive buffer. Note that data may be lost when the buffers shrink. For a new buffer size of 0 the buffer is freed and the pointer set to NULL.

Function: int svz_sock_check_request (svz_socket_t *sock)

Check for the kind of packet delimiter within sock and and assign one of the default check_request routines (one or more byte delimiters or a fixed size).

Afterwards this function will never ever be called again because the callback gets overwritten here.

Function: void svz_sock_reduce_recv (svz_socket_t *sock, int len)

Shorten the receive buffer of sock by len bytes.

Function: void svz_sock_reduce_send (svz_socket_t *sock, int len)

Reduce the send buffer of sock by len bytes.

Because libserveez manages the creation and destruction of svz_socket_t objects internally, the following API element is useful for syncronizing client-code references to those objects with those objects.

Function: void svz_sock_prefree (int addsub, svz_sock_prefree_fn fn)

Register (if addsub is non-zero), or unregister (otherwise) the function fn to be called immediately prior to a svz_socket_t being freed. fn is called with one arg sock, and should not return anything. In other words:

typedef void (svz_sock_prefree_fn) (const svz_socket_t *);

Note the const!

5.2.9 Coserver functions

This section describes the internal coserver interface of Serveez. Coservers are helper processes meant to perform blocking tasks. This is necessary because Serveez itself is single threaded. Each coserver is connected via a pair of pipes to the main thread of Serveez communicating over a simple text line protocol. Each request/response is separated by a newline character.

Function: int svz_foreach_coserver (svz_coserver_do_t *func, void *closure)

Call func for each coserver, passing additionally the second arg closure. If func returns a negative value, return immediately with that value (breaking out of the loop), otherwise, return 0.

Function: void svz_coserver_check (void)

Under woe32 check if there was any response from an active coserver. Moreover keep the coserver threads/processes alive. If one of the coservers dies due to buffer overrun or might be overloaded, start a new one.

Call this function whenever there is time, e.g., within the timeout of the select system call.

Function: void svz_coserver_destroy (int type)

Destroy specific coservers with the type type. All instances of this coserver type will be stopped.

Function: svz_coserver_t * svz_coserver_create (int type)

Create and return a single coserver with the given type type.

Function: const char * svz_coserver_type_name (const svz_coserver_t *coserver)

Return the type name of coserver.

Function: void svz_coserver_rdns_invoke (svz_address_t *addr, svz_coserver_handle_result_t cb, void *closure)

Enqueue a request for the reverse DNS coserver to resolve address addr, arranging for callback cb to be called with two args: the hostname (a string) and the opaque data closure.

Function: void svz_coserver_dns_invoke (char *host, svz_coserver_handle_result_t cb, void *closure)

Enqueue a request for the DNS coserver to resolve host, arranging for callback cb to be called with two args: the ip address in dots-and-numbers notation and the opaque data closure.

Function: void svz_coserver_ident_invoke (svz_socket_t *sock, svz_coserver_handle_result_t cb, void *closure)

Enqueue a request for the ident coserver to resolve the client identity at sock, arranging for callback cb to be called with two args: the identity (string) and the opaque data closure.

To make use of coservers, you need to start the coserver interface by calling svz_updn_all_coservers once before, and once after, entering the main server loop.

Function: int svz_updn_all_coservers (int direction)

If direction is non-zero, init coserver internals. Otherwise, finalize them. Return 0 if successful.

If direction is positive, init also starts one instance each of the builtin servers. If negative, it doesn’t.

5.2.10 Codec functions

The codec interface of the Serveez core API supplies routines for setting up socket structures to perform encoding or decoding of its receive or send buffers. It is a transparent layer of buffer transition. The interface itself tries to unify different types of codecs. In order to add a new codec the programmer needs to write some wrapper functions around the actual implementation to fulfill certain entry and exit semantics of this interface.

Function: int svz_foreach_codec (svz_codec_do_t *func, void *closure)

Call func for each codec, passing additionally the second arg closure. If func returns a negative value, return immediately with that value (breaking out of the loop), otherwise, return 0.

Function: svz_codec_t * svz_codec_get (char *description, int type)

Find an appropriate codec for the given description and type (one of either SVZ_CODEC_ENCODER or SVZ_CODEC_DECODER). Return NULL if there is no such codec registered.

Function: void svz_codec_ratio (svz_codec_t *codec, svz_codec_data_t *data)

Print a text representation of a codec’s current ratio in percent if possible.

Function: int svz_codec_register (svz_codec_t *codec)

Register codec. Does not register invalid or duplicate codecs. Return zero on success, non-zero otherwise.

Function: int svz_codec_unregister (svz_codec_t *codec)

Remove codec from the list of known codecs. Return zero if the codec could be successfully removed, non-zero otherwise.

Function: int svz_codec_sock_receive_setup (svz_socket_t *sock, svz_codec_t *codec)

Arrange for sock to decode or encode its receive data via codec. Return zero on success, non-zero otherwise.

(You need to have set the check_request method previously for this to work.)

Function: int svz_codec_sock_receive (svz_socket_t *sock)

“This routine is the new check_request callback for reading codecs. It is applied in svz_codec_sock_receive_setup. Usually it gets called whenever there is data in the receive buffer. It lets the current receive buffer be the input of the codec. The output buffer of the codec gets the new receive buffer of sock. The old check_request callback of sock gets called afterwards. When leaving this function, the receive buffer gets restored again with the bytes snipped consumed by the codec itself.” [ttn sez: huh?]

Function: int svz_codec_sock_send_setup (svz_socket_t *sock, svz_codec_t *codec)

Arrange for sock to encode or decode its send buffer via codec. Return zero on success, non-zero otherwise.

(You need to have properly set the write_socket member of sock previously for this to work.)

Function: int svz_codec_sock_send (svz_socket_t *sock)

“This is the new write_socket callback for sock which is called whenever there is data within the send buffer available and sock is scheduled for writing. It uses the current send buffer as input buffer for the codec. The output buffer of the codec is used to invoke the write_socket callback saved within svz_codec_sock_send_setup. After this the send buffer is restored again without the bytes consumed by the codec.” [ttn sez: huh?]

Function: int svz_codec_sock_disconnect (svz_socket_t *sock)

Try to release the resources of both the receiving and sending codec of sock.

This callback is used as the disconnected_socket callback of the socket structure sock. It is called by default if the codec socket structure sock gets disconnected for some external reason.

Function: svz_codec_t * svz_codec_sock_detect (svz_socket_t *sock)

Return a valid codec detected by scanning the receive buffer of sock, or NULL if no codec could be detected.

5.2.11 Server types

As already noted in the main Serveez manual a server type is the main specification of the abilities and configuration items of a server which can be instantiated. It is represented by svz_servertype_t in Serveez. It contains server specific members like its name, different callbacks, a single default configuration and a list of configuration items which determine what can be configured. Macros for setting up a new server type

When specifying a server type you also need to define configuration items for it. These items refer to addresses in the example configuration of the server type. These macros can be used to define such items.

Macro: SVZ_REGISTER_INT (name, item, defaultable)

Register a simple integer. C-type: int. The given name specifies the symbolic name of the integer and item the integer itself (not its address). The defaultable argument can be either SVZ_ITEM_DEFAULTABLE or SVZ_ITEM_NOTDEFAULTABLE.

Macro: SVZ_REGISTER_BOOL (name, item, defaultable)

Register a boolean value. C-type: int.

Macro: SVZ_REGISTER_INTARRAY (name, item, defaultable)

Register an array of integers. C-type: svz_array_t *.

Macro: SVZ_REGISTER_STR (name, item, defaultable)

Register a simple character string. C-type: char *.

Macro: SVZ_REGISTER_STRARRAY (name, item, defaultable)

Register a string array. C-type: svz_array_t *.

Macro: SVZ_REGISTER_HASH (name, item, defaultable)

Register a hash table associating strings with strings only. C-type: svz_hash_t *.

Macro: SVZ_REGISTER_PORTCFG (name, item, defaultable)

Register a port configuration. C-type: svz_portcfg_t *.


Indicate the end of the list of configuration items. It is the only mandatory item you need to specify in an example server type configuration.

Macro: SVZ_CONFIG_DEFINE (description, config, prototypes)

Expand to a data structure that properly associates the example configuration config with the name description and its configuration items prototypes, for use within a server type definition. General server type functionality

The following set of functions are used to manage the list of known server types in the Serveez core library. Serveez itself uses some of these functions to register its builtin server types.

Function: int svz_foreach_servertype (svz_servertype_do_t *func, void *closure)

Call func for each servertype, passing additionally the second arg closure. If func returns a negative value, return immediately with that value (breaking out of the loop), otherwise, return 0.

Function: void svz_servertype_add (svz_servertype_t *server)

Add the server type server to the currently registered servers.

Function: svz_servertype_t * svz_servertype_get (char *name, int dynamic)

Find a servertype definition by its short name. If dynamic is set to non-zero, try to load a shared library that provides that servertype. Return NULL if no server with the given variable prefix name has been found.

Function: svz_servertype_t * svz_servertype_find (svz_server_t *server)

Find a given server instances server server type. Return NULL if there is no such server type (which should never occur since a server is a child of a server type). Dynamic server loading

The core API of Serveez is able to register server types dynamically at runtime. It uses the dynamic linker capabilities of the underlying operating system to load shared libraries (or DLLs on Win32). This has been successfully tested on Windows and GNU/Linux. Other systems are supported but yet untested. Please tell us if you notice misbehaviour of any sort.

Function: void svz_dynload_path_set (svz_array_t *paths)

Set the additional search paths for the serveez library. The given array of strings gets svz_freed.

Function: svz_array_t * svz_dynload_path_get (void)

Create an array of strings containing each an additional search path. The loadpath is hold in the environment variable ‘SERVEEZ_LOAD_PATH’ which can be set from outside the library or modified using svz_dynload_path_set. The returned array needs to be destroyed after usage.

5.2.12 Server functions

A server in Serveez is an instantiated (configured) server type. It is merely a copy of a specific server type with a unique server name, and is represented by svz_server_t in the core library. Server functionality

This section contains functions dealing with the list of known servers in the core library of Serveez, also with the basics like creation and destruction of such servers.

Function: void svz_foreach_server (svz_server_do_t *func, void *closure)

Call func for each server, passing additionally the second arg closure.

Function: svz_server_t * svz_server_find (void *cfg)

Find a server instance by the given configuration structure cfg. Return NULL if there is no such configuration in any server instance.

Function: svz_array_t * svz_server_clients (svz_server_t *server)

Return a list of clients (socket structures) which are associated with the given server instance server. If there is no such socket, return NULL. Caller should svz_array_destroy the returned array.

Function: svz_server_t * svz_server_get (char *name)

Get the server instance with the given instance name name. Return NULL if there is no such server yet.

Function: int svz_updn_all_servers (int direction)

If direction is non-zero, run the initializers of all servers, returning -1 if some server did not think it is a good idea to run. Otherwise, run the local finalizers for all server instances. Configuration

These functions provide an interface for configuring a server. They are used to create and modify the default configuration of a server type in order to create a server configuration.

Function: int svz_config_type_instantiate (char *type, char *name, char *instance, void *options, svz_config_accessor_t *accessor, size_t ebufsz, char *ebuf)

Instantiate a configurable type. The type argument specifies the configurable type name, name the name of the type (in the domain of the configurable type) and instance the instance name of the type. Return zero on success, otherwise -1.

Function: void svz_config_free (svz_config_prototype_t *prototype, void *cfg)

Release the configuration cfg of the given configuration prototype prototype. If cfg is NULL, do nothing.

Function: void * svz_collect (int type, size_t count, void *data)

Create a collection of type, given the count items of data. Valid values of type are one of: SVZ_INTARRAY, SVZ_STRARRAY, SVZ_STRHASH. For a string hash, data should be alternating keys and values; the returned hash table will have count / 2 elements. The C type of data for an int array should be int[], and for string array or hash it should be char*[]. On error (either bad type or odd count for string hash), return NULL.

Here are some convenience macros for svz_collect:


Return an integer array svz_array_t * created from int cvar[].


Return a string array svz_array_t * created from char *cvar[].


Return a string hash svz_hash_t * created from char *cvar[]. Bindings

The following functionality represents the relationship between port configurations as described in Port configurations and server instances. When binding a server to a specific port configuration the core library creates listeners as needed by itself.

Function: int svz_server_bind (svz_server_t *server, svz_portcfg_t *port)

Bind the server instance server to the port configuration port if possible. Return non-zero on errors, otherwise zero. It might occur that a single server is bound to more than one network port if, e.g., the TCP/IP address is specified by ‘*’ (asterisk) since this gets expanded to the known list of interfaces.

Function: svz_array_t * svz_server_portcfgs (svz_server_t *server)

Return an array of port configurations to which the server instance server is currently bound to, or NULL if there is no such binding. Caller should svz_array_destroy the returned array when done.

Function: svz_array_t * svz_server_listeners (svz_server_t *server)

Return an array of listening socket structures to which the server instance server is currently bound to, or NULL if there is no such binding. Caller should svz_array_destroy the returned array when done.

Function: svz_array_t * svz_sock_servers (svz_socket_t *sock)

Return the array of server instances bound to the listening sock, or NULL if there are no bindings. Caller should svz_array_destroy the returned array when done.

Function: int svz_binding_contains_server (svz_socket_t *sock, svz_server_t *server)

Checks whether the server instance server is bound to the server socket structure sock. Return one if so, otherwise zero.

Function: size_t svz_pp_server_bindings (char *buf, size_t size, svz_server_t *server)

Format a space-separated list of current port configuration bindings for server into buf, which has size bytes. The string is guaranteed to be nul-terminated. Return the length (at most size - 1) of the formatted string.

Next: , Previous: , Up: Server functions   [Contents][Index] Server core

Variable: svz_t_handle svz_child_died

Set to a non-zero value whenever the server receives a SIGCHLD signal.

Function: int svz_shutting_down_p (void)

Return non-zero if the core is in the process of shutting down (typically as a result of a signal).

Function: int svz_foreach_socket (svz_socket_do_t *func, void *closure)

Call func for each socket, passing additionally the second arg closure. If func returns a negative value, return immediately with that value (breaking out of the loop), otherwise, return 0.

Function: svz_socket_t * svz_sock_find (int id, int version)

Return the socket structure for the socket id id and the version version, or NULL if no such socket exists. If version is -1 it is not checked.

Function: int svz_sock_schedule_for_shutdown (svz_socket_t *sock)

Mark socket sock as killed. That means that no further operations except disconnecting and freeing are allowed. All marked sockets will be deleted once the server loop is through.

Function: int svz_sock_enqueue (svz_socket_t *sock)

Enqueue the socket sock into the list of sockets handled by the server loop.

Function: void svz_sock_setparent (svz_socket_t *child, svz_socket_t *parent)

Set the child socket’s parent to parent.

This should be called whenever a listener accepts a connection and creates a new child socket.

Function: svz_socket_t * svz_sock_getparent (svz_socket_t *child)

Return the child socket’s parent socket structure, or NULL if this socket does not exist anymore. This might happen if a listener dies for some reason.

Function: void svz_sock_setreferrer (svz_socket_t *sock, svz_socket_t *referrer)

Set the referring socket structure of sock to referrer. If referrer is NULL the reference will be invalidated.

This can be used to create some relationship between two socket structures.

Function: svz_socket_t * svz_sock_getreferrer (svz_socket_t *sock)

Get the referrer of the socket structure sock. Return NULL if there is no such socket.

Function: svz_portcfg_t * svz_sock_portcfg (svz_socket_t *sock)

Return the parent’s port configuration of sock, or NULL if the given socket has no parent, i.e. is a listener. Server loop

This section describes the main server loop functionality. There two modes of operation. The default mode as used in Serveez is to jump into the loop and wait until the core library drops out of it. In the other mode, the caller tells the Serveez core library to scan (and process) its socket chain once and return immediately. Thus, caller is able to issue additional functionality in between each pass, useful if such functionality cannot be handled within the timers (notifiers) of servers and sockets.

Function: void svz_loop_pre (void)

Initialize top-of-cycle state.

Call this function once before using svz_loop_one.

Function: void svz_loop_post (void)

Clean up bottom-of-cycle state.

Call this function once after using svz_loop_one.

Function: void svz_loop (void)

Loop, serving. In other words, handle all signals, incoming and outgoing connections and listening server sockets.

Function: void svz_loop_one (void)

Handle all things once.

This function is called regularly by svz_loop. Server sockets

This section deals with creating and handling listeners. These functions provide the default routines invoked when accepting a new connection on a listener. This is necessary for connection oriented protocols (TCP and named pipes) only.

[FIXME: All funcs internalized! Write something else here!]

5.2.13 Port configurations

A port configuration is a structure defining a network or file system configuration. Depending on the type of a server, it can be bound to one or more port configurations. There are two major types of port configurations: connection oriented (TCP and PIPE), and packet oriented (ICMP, UDP and RAW).

Function: struct sockaddr_in * svz_portcfg_addr (svz_portcfg_t *port)

Return the pointer of the sockaddr_in structure of the given port configuration port if it is a network port configuration. Otherwise return NULL.

Function: in_port_t svz_portcfg_port (svz_portcfg_t *port)

Return the UDP or TCP port of the given port configuration or zero if it neither TCP nor UDP.

Function: char * svz_portcfg_ipaddr (svz_portcfg_t *port)

Return the pointer to the ip address ipaddr of the given port configuration port if it is a network port configuration. Otherwise return NULL.

Function: char * svz_portcfg_device (svz_portcfg_t *port)

Return the network device name stored in the given port configuration port if it is a network port configuration. Return NULL if there is no such device set or if the port configuration is not a network port configuration.

Serveez maintains an internal list of port configurations, with each identified by its name. When you bind a server to a port configuration, it does not get bound to a certain name but to its content. If there are two or more port configuration specifying the same network or file system configuration just a single one gets actually used.

Function: svz_portcfg_t * svz_portcfg_create (void)

Create a new blank port configuration.

Function: int svz_portcfg_equal (svz_portcfg_t *a, svz_portcfg_t *b)

Check if two given port configurations structures are equal, i.e. specifying the same network port or pipe files. Return SVZ_PORTCFG_EQUAL if a and b are identical, SVZ_PORTCFG_MATCH if the network address of either port configuration contains the other (INADDR_ANY match), and otherwise SVZ_PORTCFG_NOMATCH or possibly SVZ_PORTCFG_CONFLICT.

Function: svz_portcfg_t * svz_portcfg_add (char *name, svz_portcfg_t *port)

Add the given port configuration port associated with the name name to the list of known port configurations. Return NULL on errors. If the return port configuration equals the given port configuration the given one has been successfully added.

Function: svz_portcfg_t * svz_portcfg_get (char *name)

Return the port configuration associated with the given name name. Return NULL on errors.

Function: void svz_portcfg_destroy (svz_portcfg_t *port)

Make the given port configuration port completely unusable, removing it from the list of known port configurations. Do nothing if port is NULL.

Function: int svz_portcfg_mkaddr (svz_portcfg_t *this)

Construct the sockaddr_in fields from the ipaddr field. Return zero if it worked. If it does not work, the ipaddr field did not consist of an ip address in dotted decimal form.

Function: svz_portcfg_t * svz_portcfg_dup (svz_portcfg_t *port)

Make a copy of the given port configuration port.

5.2.14 Boot functions

The most important functions are svz_boot and svz_halt which must be the first and the last call to the core API.

Function: void svz_boot (char const *client)

Initialize the core library. client is typically a program’s argv[0]. If NULL, take it to be ‘anonymous’.

Function: long svz_uptime (void)

Return the number of seconds since svz_boot was called, or -1 if svz_boot has not yet been called.

Function: void svz_halt (void)

Finalization of the core library. Runtime parameters

There are several runtime parameters indicating the abilities of the libserveez core API:


The log-level verbosity.


Maxium number of clients allowed to connect.

These are manipulated by svz_runparm and two convenience macros, both of which accept nick, a C token without the prefix ‘SVZ_RUNPARM_’ (e.g., VERBOSITY).

Function: int svz_runparm (int a, int b)

Set or get a runtime parameter. If a is -1, return the value of runtime parameter b. If a specifies a runtime parameter, set it to b and return 0. Otherwise, return -1.

Macro: SVZ_RUNPARM (nick)

Return the value of runtime parameter nick.

Macro: SVZ_RUNPARM_X (nick, val)

Set the runtime paramater nick to have value val, an integer.

5.2.15 Network interface functions

The network interface functions of the Serveez core API allow access to the network devices on your system. The system administrator can set up these devices to be bound to different Internet addresses and thereby split the network configuration into different domains. Thus, the system is able to separate the traffic of different networks. If set up correctly, Serveez can follow these rules.

Function: int svz_foreach_interface (svz_interface_do_t *func, void *closure)

Call func for each interface, passing additionally the second arg closure. If func returns a negative value, return immediately with that value (breaking out of the loop), otherwise, return 0.

Function: int svz_interface_add (size_t index, char *desc, int family, const void *bits, int detected)

Add a network interface to the current list of known interfaces. Drop duplicate entries. The given arguments index specifies the network interface index number, desc an interface desription, family an address-family (e.g., AF_INET), bits the address data in network-byte order, and the detected flag if the given network interface has been detected by Serveez itself or not.

5.2.16 Useful Windows functions

Serveez is meant to run on Windows systems as well (with some restrictions of course). These functions are available with the Windows implementation of the Serveez core API only. They allow access to the Windows registry database and some other useful things.

Function: int svz_windoze_daemon_control (char *prog)

If prog is non-NULL, start the daemon thread with it. Otherwise (if prog is NULL), stop the daemon thread. Return 0 on success, -1 on failure.

Function: WCHAR * svz_windoze_asc2uni (CHAR *asc)

Convert an ASCII string into a UNICODE string.

Function: CHAR * svz_windoze_uni2asc (WCHAR *unicode)

Convert a UNICODE string into an ASCII string.

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6 Porting issues

Serveez was always designed with an eye on maximum portability. Autoconf and Automake have done a great job at this. A lot of #define’s help to work around some of the different Unix’ oddities. Have a look at config.h for a complete list of all these conditionals.

Most doubtful might be the Win32 port. There are two different ways of compiling Serveez on Win32: Cygwin and MinGW. The Cygwin version of Serveez depends on the Unix emulation layer DLL cygwin1.dll. Both versions work but it is preferable to use MinGW for performance reasons. The Cygwin version is slow and limited to a very low number (some 64) of open files/network connections.2

There are major differences between the Win32 and Unix implementations due to the completely different API those systems provide.

Processes and Threads

Because process communication is usually done by a pair of unidirectional pipes we chose that method in order to implement the coservers in Unix. The Win32 implementation are threads which are still part of the main process.

Sockets and Handles

On Win32 systems there is a difference in network sockets and file descriptors. Thus we had to implement quite a complex main socket loop.

Named Pipes

Both systems Unix and Win32 do provide this functionality (Windows NT 4.0 and above). The main differences here are the completely different APIs. On a common Unix you create a named pipe within the filesystem via mkfifo. On Win32 you have to CreateNamedPipe which will create some special network device. A further difference is what you can do with these pipes. On Win32 systems this ‘network device’ is valid on remote machines. Named pipes on Unix are unidirectional, on Win32 they are bidirectional and instantiatable.

Winsock Versions

There are some difference between the original Winsock 1.1 API and the new version 2.2.x. In a nutshell, WinSock 2 is WinSock 1.1 on steroids, it’s a superset of 1.1’s APIs and architecture. In addition to its new features, it also clarifies existing ambiguities in the 1.1 WinSock specification and adds new extensions that take advantage of operating system features and enhance application performance and efficiency. Finally, WinSock 2 includes a number of new protocol-specific extensions. These extensions –such as multicast socket options– are relegated to a separate annex, since the main WinSock 2 protocol specification is protocol-independent.

The Winsock DLL and import library for version 1.1 are wsock32.dll and wsock32.lib and for version 2.2 it is ws2_32.dll and ws2_32.lib. Serveez is currently using version 2.2.

The Winsock API is still a bit buggy. Connected datagram behaviors are not pertinent to any WinSock 2 features, but to generic WinSock. On Win95 it is possible to use recvfrom/WSARecvFrom on a “connected” UDP socket, but on NT4 recvfrom/WSARecvFrom fail with 10056 (WSAEISCONN). NOTE: sendto/WSASendTo fail with WSAEISCONN on both (which I do not see any reason for, but anyway ...).

Raw sockets on Windows systems

Raw sockets require Winsock 2. To use them under Windows NT/2000, you must be logged in as an Administrator. On any other Microsoft’s we were trying to use the ICMP.DLL (an idiotic and almost useless API) without success. Microsoft says they will replace it as soon as something better comes along. (Microsoft’s been saying this since the Windows 95 days, however, yet this functionality still exists in Windows 2000.) It seems like you cannot send ICMP or even raw packets from the userspace of Windows (except via the ICMP.DLL which is limited to echo requests). We also noticed that you cannot receive any packets previously sent. The only thing which works on all Windows systems (9x/ME/NT/2000/XP) is receiving packets the “kernel” itself generated (like echo replies). One good thing we noticed about Windows 2000 is that the checksums of fragmented ICMP packets get correctly recalculated. That is not the case in the current Linux kernels.


To use the Win32 Winsock in the Cygwin port, you just need to #define Win32_Winsock and #include "windows.h" at the top of your source file(s). You will also want to add -lwsock32 to the compiler’s command line so you link against libwsock32.a.

What preprocessor macros do I need to know about ? We use _WIN32 to signify access to the Win32 API and __CYGWIN__ for access to the Cygwin environment provided by the dll. We chose _WIN32 because this is what Microsoft defines in VC++ and we thought it would be a good idea for compatibility with VC++ code to follow their example. We use _MFC_VER to indicate code that should be compiled with VC++.

Why we do not use pipes for coservers ? Windows differentiates between sockets and file descriptors, that is why you can not select file descriptors. Please close the pipe’s descriptors via CloseHandle and not closesocket, because this will fail.

The C run-time libraries have a preset limit for the number of files that can be open at any one time. The limit for applications that link with the single-thread static library (LIBC.LIB) is 64 file handles or 20 file streams. Applications that link with either the static or dynamic multithread library (LIBCMT.LIB or MSVCRT.LIB and MSVCRT.DLL), have a limit of 256 file handles or 40 file streams. Attempting to open more than the maximum number of file handles or file streams causes program failure.

As far as I know, one of the big limitations of Winsock is that the SOCKET type is *not* equivalent to file descriptor. It is however with BSD and POSIX sockets. That is one of the major reasons for using a separate data type, SOCKET, not an int, a typical type for a file descriptor. This implies that you cannot mix SOCKETs and stdio, sorry. This is the case when you use -mno-cygwin.

Actually they are regular file handles, just like any other. There is a bug in all 9x/kernel32 libc/msv/crtdll interface implementations GetFileType returns TYPE_UNKNOWN for socket handles. Since this is AFAIK the only unknown type there is, you know you have a socket handle. There is a fix in the more recent perl distributions that you can use as a general solution. -loldnames -lperlcrt -lmsvcrt will get you TYPE_CHAR for socket handles.

Now follows the list on which operating systems and architectures Serveez has been build and tested successfully.

7 Bibliography

This section contain some of the documents and resources we read and used to implement various parts of this package. They appear in no specific order.

  1. RFC 760
    The Internet Protocol
  2. RFC 1071
    Computing the Internet Checksum
  3. RFC 1413
    Identification Protocol
  4. RFC 1459
    Internet Relay Chat Protocol
  5. RFC 1945
    Hypertext Transfer Protocol – HTTP/1.0
  6. RFC 2068
    Hypertext Transfer Protocol – HTTP/1.1
  7. RFC 2616
    Hypertext Transfer Protocol – HTTP/1.1
  8. RFC 768
    User Datagram Protocol
  9. RFC 791
    Internet Protocol
  10. RFC 777
    Internet Control Message Protocol
    Home of the MinGW (Minimal GNU for Windows) project
    The Gnutella Protocol
    The official EFNet site (includes Hybrid IRC server)
    Winsock Development Information
    Winsock Programmer’s FAQ

Next: , Previous: , Up: GNU Serveez   [Contents][Index]

Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.


    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

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    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

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    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

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    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

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    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

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    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See

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    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
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  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
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If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

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If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.


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Index Entry  Section

binary->list: Guile servers
binary->string: Guile servers
binary-char-ref: Guile servers
binary-char-set!: Guile servers
binary-concat!: Guile servers
binary-int-ref: Guile servers
binary-int-set!: Guile servers
binary-length: Guile servers
binary-long-ref: Guile servers
binary-long-set!: Guile servers
binary-ref: Guile servers
binary-reverse: Guile servers
binary-reverse!: Guile servers
binary-search: Guile servers
binary-set!: Guile servers
binary-short-ref: Guile servers
binary-short-set!: Guile servers
binary-subset: Guile servers
binary?: Guile servers
bind-servers!: Bind servers to ports
bind-tcp-port-range!: Bind servers to ports
bind-udp-port-range!: Bind servers to ports

check-oob-request: Guile servers
check-request: Guile servers
connect-socket: Guile servers
create-tcp-port!: Bind servers to ports
create-udp-port!: Bind servers to ports

define-servertype!: Guile servers
detect-proto: Guile servers
disconnected: Guile servers

embedding: Embedding
endrpcent: Bind servers to ports

finalize: Guile servers
fs: Bind servers to ports

getrpc: Guile servers
getrpcbyname: Bind servers to ports
getrpcbynumber: Bind servers to ports
getrpcent: Bind servers to ports
global-finalize: Guile servers
global-init: Guile servers

handle-request: Guile servers

idle: Guile servers
info-client: Guile servers
info-server: Guile servers
init: Guile servers
interface-add!: Bind servers to ports

kicked: Guile servers

libserveez-features: Guile servers
list->binary: Guile servers
loadpath-add!: Bind servers to ports

notify: Guile servers

portmap: Guile servers
portmap-list: Guile servers
println: Bind servers to ports
printsln: Bind servers to ports

reset: Guile servers

serveez-exceptions: Guile servers
serveez-interfaces: Guile servers
serveez-load: Bind servers to ports
serveez-loadpath: Guile servers
serveez-maxsockets: Bind servers to ports
serveez-nuke: Guile servers
serveez-passwd: Bind servers to ports
serveez-port?: Guile servers
serveez-server?: Guile servers
serveez-servertype?: Guile servers
serveez-verbosity: Bind servers to ports
setrpc: Guile servers
setrpcent: Bind servers to ports
string->binary: Guile servers
svz:coserver:dns: Guile servers
svz:coserver:ident: Guile servers
svz:coserver:reverse-dns: Guile servers
svz:read-file: Guile servers
svz:server:clients: Guile servers
svz:server:config-ref: Guile servers
svz:server:listeners: Guile servers
svz:server?: Guile servers
svz:sock:boundary: Guile servers
svz:sock:check-oob-request: Guile servers
svz:sock:check-request: Guile servers
svz:sock:connect: Guile servers
svz:sock:disconnected: Guile servers
svz:sock:final-print: Guile servers
svz:sock:find: Guile servers
svz:sock:floodprotect: Guile servers
svz:sock:handle-request: Guile servers
svz:sock:ident: Guile servers
svz:sock:idle: Guile servers
svz:sock:idle-counter: Guile servers
svz:sock:kicked: Guile servers
svz:sock:local-address: Guile servers
svz:sock:no-delay: Guile servers
svz:sock:parent: Guile servers
svz:sock:print: Guile servers
svz:sock:protocol: Guile servers
svz:sock:receive-buffer: Guile servers
svz:sock:receive-buffer-reduce: Guile servers
svz:sock:receive-buffer-size: Guile servers
svz:sock:referrer: Guile servers
svz:sock:remote-address: Guile servers
svz:sock:send-buffer: Guile servers
svz:sock:send-buffer-size: Guile servers
svz:sock:send-oob: Guile servers
svz:sock:server: Guile servers
svz:sock:trigger: Guile servers
svz:sock:trigger-condition: Guile servers
svz:sock?: Guile servers
svz_address_copy: svz_address_t
svz_address_family: svz_address_t
svz_address_make: svz_address_t
svz_address_same: svz_address_t
svz_address_to: svz_address_t
svz_array_add: Array
svz_array_create: Array
svz_array_del: Array
svz_array_destroy: Array
svz_array_foreach: Array
svz_array_get: Array
svz_array_set: Array
svz_array_size: Array
svz_atoi: Utility functions
svz_binding_contains_server: Server binding
svz_boot: Booting
svz_calloc: Memory management
svz_child_died: Server core
svz_close: Core functions
svz_closehandle: Pipe connections
svz_closesocket: Core functions
svz_codec_get: Codec functions
svz_codec_ratio: Codec functions
svz_codec_register: Codec functions
svz_codec_sock_detect: Codec functions
svz_codec_sock_disconnect: Codec functions
svz_codec_sock_receive: Codec functions
svz_codec_sock_receive_setup: Codec functions
svz_codec_sock_send: Codec functions
svz_codec_sock_send_setup: Codec functions
svz_codec_unregister: Codec functions
svz_collect: Server configuration
SVZ_COLLECT_INTARRAY: Server configuration
SVZ_COLLECT_STRARRAY: Server configuration
SVZ_COLLECT_STRHASH: Server configuration
SVZ_CONFIG_DEFINE: Macros for setting up a new server type
svz_config_free: Server configuration
svz_config_type_instantiate: Server configuration
svz_coserver_check: Coserver functions
svz_coserver_create: Coserver functions
svz_coserver_destroy: Coserver functions
svz_coserver_dns_invoke: Coserver functions
svz_coserver_ident_invoke: Coserver functions
svz_coserver_rdns_invoke: Coserver functions
svz_coserver_type_name: Coserver functions
svz_dynload_path_get: Dynamic server loading
svz_dynload_path_set: Dynamic server loading
svz_envblock_add: Passthrough connections
svz_envblock_create: Passthrough connections
svz_envblock_default: Passthrough connections
svz_envblock_destroy: Passthrough connections
svz_envblock_get: Passthrough connections
svz_envblock_setup: Passthrough connections
svz_fclose: Core functions
svz_fd_cloexec: Core functions
svz_fopen: Core functions
svz_foreach_codec: Codec functions
svz_foreach_coserver: Coserver functions
svz_foreach_interface: Interface
svz_foreach_server: Server functionality
svz_foreach_servertype: General server type functionality
svz_foreach_socket: Server core
svz_free: Memory management
svz_fstat: Core functions
svz_getcwd: Utility functions
svz_get_curalloc: Memory management
svz_halt: Booting
svz_hash_configure: Hashtable
svz_hash_contains: Hashtable
svz_hash_create: Hashtable
svz_hash_delete: Hashtable
svz_hash_destroy: Hashtable
svz_hash_exists: Hashtable
svz_hash_foreach: Hashtable
svz_hash_get: Hashtable
svz_hash_put: Hashtable
svz_hash_size: Hashtable
svz_hexdump: Utility functions
svz_icmp_connect: ICMP sockets
svz_icmp_send_control: ICMP sockets
svz_icmp_write: ICMP sockets
svz_inet_aton: Core functions
svz_inet_ntoa: Core functions
svz_interface_add: Interface
svz_invalidate_handle: Pipe connections
svz_invalid_handle_p: Pipe connections
svz_itoa: Utility functions
svz_library_features: Library features
svz_log: Utility functions
svz_log_net_error: Utility functions
svz_log_setfile: Utility functions
svz_log_sys_error: Utility functions
svz_loop: Server loop
svz_loop_one: Server loop
svz_loop_post: Server loop
svz_loop_pre: Server loop
svz_malloc: Memory management
svz_mingw_at_least_nt4_p: Utility functions
svz_mingw_child_dead_p: Passthrough connections
svz_most_recent_dead_child_p: Passthrough connections
svz_open: Core functions
svz_openfiles: Utility functions
svz_pipe_connect: Pipe connections
svz_pipe_create: Pipe connections
svz_pipe_create_pair: Pipe connections
svz_portcfg_add: Port config funcs
svz_portcfg_addr: Port config funcs
svz_portcfg_create: Port config funcs
svz_portcfg_destroy: Port config funcs
svz_portcfg_device: Port config funcs
svz_portcfg_dup: Port config funcs
svz_portcfg_equal: Port config funcs
svz_portcfg_get: Port config funcs
svz_portcfg_ipaddr: Port config funcs
svz_portcfg_mkaddr: Port config funcs
svz_portcfg_port: Port config funcs
SVZ_PP_ADDR: svz_address_t
svz_pp_address: svz_address_t
svz_pp_addr_port: svz_address_t
SVZ_PP_ADDR_PORT: svz_address_t
svz_pp_server_bindings: Server binding
svz_realloc: Memory management
SVZ_REGISTER_BOOL: Macros for setting up a new server type
SVZ_REGISTER_END: Macros for setting up a new server type
SVZ_REGISTER_HASH: Macros for setting up a new server type
SVZ_REGISTER_INT: Macros for setting up a new server type
SVZ_REGISTER_INTARRAY: Macros for setting up a new server type
SVZ_REGISTER_PORTCFG: Macros for setting up a new server type
SVZ_REGISTER_STR: Macros for setting up a new server type
SVZ_REGISTER_STRARRAY: Macros for setting up a new server type
svz_runparm: Booting
svz_sendfile: Core functions
svz_servertype_add: General server type functionality
svz_servertype_find: General server type functionality
svz_servertype_get: General server type functionality
svz_server_bind: Server binding
svz_server_clients: Server functionality
svz_server_find: Server functionality
svz_server_get: Server functionality
svz_server_listeners: Server binding
svz_server_portcfgs: Server binding
SVZ_SET_ADDR: svz_address_t
svz_set_mm_funcs: Memory management
svz_shutting_down_p: Server core
svz_socket_unavailable_error_p: Utility functions
svz_sock_check_request: Socket management
svz_sock_enqueue: Server core
svz_sock_find: Server core
svz_sock_getparent: Server core
svz_sock_getreferrer: Server core
svz_sock_nconnections: Socket management
svz_sock_portcfg: Server core
svz_sock_prefree: Socket management
svz_sock_prefree_fn: Socket management
svz_sock_printf: Socket management
svz_sock_process: Passthrough connections
svz_sock_reduce_recv: Socket management
svz_sock_reduce_send: Socket management
svz_sock_resize_buffers: Socket management
svz_sock_schedule_for_shutdown: Server core
svz_sock_servers: Server binding
svz_sock_setparent: Server core
svz_sock_setreferrer: Server core
svz_sock_write: Socket management
svz_strdup: Memory management
svz_sys_strerror: Utility functions
svz_sys_version: Utility functions
svz_tcp_connect: TCP sockets
svz_tcp_cork: Core functions
svz_tcp_nodelay: Core functions
svz_tcp_read_socket: TCP sockets
svz_tcp_send_oob: TCP sockets
svz_time: Utility functions
svz_tolower: Utility functions
svz_udp_connect: UDP sockets
svz_udp_write: UDP sockets
svz_updn_all_coservers: Coserver functions
svz_updn_all_servers: Server functionality
svz_uptime: Booting
svz_windoze_asc2uni: Windoze
svz_windoze_daemon_control: Windoze
svz_windoze_uni2asc: Windoze

trigger: Guile servers
trigger-condition: Guile servers

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that is, if your system supports it


This was written circa 2003—maybe the situation is now improved.