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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);
}