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16.9.6 Byte Stream Socket Example

Here is an example client program that makes a connection for a byte stream socket in the Internet namespace. It doesn't do anything particularly interesting once it has connected to the server; it just sends a text string to the server and exits.

This program uses init_sockaddr to set up the socket address; see Inet Example.

     
     #include <stdio.h>
     #include <errno.h>
     #include <stdlib.h>
     #include <unistd.h>
     #include <sys/types.h>
     #include <sys/socket.h>
     #include <netinet/in.h>
     #include <netdb.h>
     
     #define PORT            5555
     #define MESSAGE         "Yow!!! Are we having fun yet?!?"
     #define SERVERHOST      "www.gnu.org"
     
     void
     write_to_server (int filedes)
     {
       int nbytes;
     
       nbytes = write (filedes, MESSAGE, strlen (MESSAGE) + 1);
       if (nbytes < 0)
         {
           perror ("write");
           exit (EXIT_FAILURE);
         }
     }
     
     
     int
     main (void)
     {
       extern void init_sockaddr (struct sockaddr_in *name,
                                  const char *hostname,
                                  uint16_t port);
       int sock;
       struct sockaddr_in servername;
     
       /* Create the socket. */
       sock = socket (PF_INET, SOCK_STREAM, 0);
       if (sock < 0)
         {
           perror ("socket (client)");
           exit (EXIT_FAILURE);
         }
     
       /* Connect to the server. */
       init_sockaddr (&servername, SERVERHOST, PORT);
       if (0 > connect (sock,
                        (struct sockaddr *) &servername,
                        sizeof (servername)))
         {
           perror ("connect (client)");
           exit (EXIT_FAILURE);
         }
     
       /* Send data to the server. */
       write_to_server (sock);
       close (sock);
       exit (EXIT_SUCCESS);
     }