glibc/manual/examples/inetcli.c

/* Byte Stream Socket Example
   Copyright (C) 1991-2019 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, see <http://www.gnu.org/licenses/>.
*/

#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);
}