send function is declared in the header file
sys/socket.h. If your flags argument is zero, you can just
as well use
write instead of
send; see Input and Output Primitives. If the socket was connected but the connection has broken,
you get a
SIGPIPE signal for any use of
write (see Miscellaneous Signals).
Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.
send function is like
write, but with the additional
flags flags. The possible values of flags are described
in Socket Data Options.
This function returns the number of bytes transmitted, or
failure. If the socket is nonblocking, then
write) can return after sending just part of the data.
See File Status Flags, for information about nonblocking mode.
Note, however, that a successful return value merely indicates that the message has been sent without error, not necessarily that it has been received without error.
errno error conditions are defined for this function:
The socket argument is not a valid file descriptor.
The operation was interrupted by a signal before any data was sent. See Primitives Interrupted by Signals.
The descriptor socket is not a socket.
The socket type requires that the message be sent atomically, but the message is too large for this to be possible.
Nonblocking mode has been set on the socket, and the write operation
would block. (Normally
send blocks until the operation can be
There is not enough internal buffer space available.
You never connected this socket.
This socket was connected but the connection is now broken. In this
send generates a
SIGPIPE signal first; if that
signal is ignored or blocked, or if its handler returns, then
send fails with
This function is defined as a cancellation point in multi-threaded programs, so one has to be prepared for this and make sure that allocated resources (like memory, file descriptors, semaphores or whatever) are freed even if the thread is canceled.