glibc/manual/examples/filesrv.c

/* Datagram Socket Example
   Copyright (C) 1991-2022 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 <https://www.gnu.org/licenses/>.
*/

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/un.h>

#define SERVER	"/tmp/serversocket"
#define MAXMSG	512

int
main (void)
{
  int sock;
  char message[MAXMSG];
  struct sockaddr_un name;
  size_t size;
  int nbytes;

  /* Remove the filename first, it's ok if the call fails */
  unlink (SERVER);

  /* Make the socket, then loop endlessly. */
  sock = make_named_socket (SERVER);
  while (1)
    {
      /* Wait for a datagram. */
      size = sizeof (name);
      nbytes = recvfrom (sock, message, MAXMSG, 0,
			 (struct sockaddr *) & name, &size);
      if (nbytes < 0)
	{
	  perror ("recfrom (server)");
	  exit (EXIT_FAILURE);
	}

      /* Give a diagnostic message. */
      fprintf (stderr, "Server: got message: %s\n", message);

      /* Bounce the message back to the sender. */
      nbytes = sendto (sock, message, nbytes, 0,
		       (struct sockaddr *) & name, size);
      if (nbytes < 0)
	{
	  perror ("sendto (server)");
	  exit (EXIT_FAILURE);
	}
    }
}