The GNU C Library - Byte Stream Example

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.

	#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      "churchy.gnu.ai.mit.edu"
	
	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,
	                             unsigned short int 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);
	}