1  /* Datagram Socket Example
       2     Copyright (C) 1991-2023 Free Software Foundation, Inc.
       3  
       4     This program is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU General Public License
       6     as published by the Free Software Foundation; either version 2
       7     of the License, or (at your option) any later version.
       8  
       9     This program is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12     GNU General Public License for more details.
      13  
      14     You should have received a copy of the GNU General Public License
      15     along with this program; if not, see <https://www.gnu.org/licenses/>.
      16  */
      17  
      18  #include <stdio.h>
      19  #include <errno.h>
      20  #include <stdlib.h>
      21  #include <sys/socket.h>
      22  #include <sys/un.h>
      23  
      24  #define SERVER	"/tmp/serversocket"
      25  #define MAXMSG	512
      26  
      27  int
      28  main (void)
      29  {
      30    int sock;
      31    char message[MAXMSG];
      32    struct sockaddr_un name;
      33    size_t size;
      34    int nbytes;
      35  
      36    /* Remove the filename first, it's ok if the call fails */
      37    unlink (SERVER);
      38  
      39    /* Make the socket, then loop endlessly. */
      40    sock = make_named_socket (SERVER);
      41    while (1)
      42      {
      43        /* Wait for a datagram. */
      44        size = sizeof (name);
      45        nbytes = recvfrom (sock, message, MAXMSG, 0,
      46  			 (struct sockaddr *) & name, &size);
      47        if (nbytes < 0)
      48  	{
      49  	  perror ("recfrom (server)");
      50  	  exit (EXIT_FAILURE);
      51  	}
      52  
      53        /* Give a diagnostic message. */
      54        fprintf (stderr, "Server: got message: %s\n", message);
      55  
      56        /* Bounce the message back to the sender. */
      57        nbytes = sendto (sock, message, nbytes, 0,
      58  		       (struct sockaddr *) & name, size);
      59        if (nbytes < 0)
      60  	{
      61  	  perror ("sendto (server)");
      62  	  exit (EXIT_FAILURE);
      63  	}
      64      }
      65  }