manual/examples/inetcli.c

   1 /* Byte Stream 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 <unistd.h>
  22 #include <sys/types.h>
  23 #include <sys/socket.h>
  24 #include <netinet/in.h>
  25 #include <netdb.h>
  26
  27 #define PORT            5555
  28 #define MESSAGE         "Yow!!! Are we having fun yet?!?"
  29 #define SERVERHOST      "www.gnu.org"
  30
  31 void
  32 write_to_server (int filedes)
  33 {
  34   int nbytes;
  35
  36   nbytes = write (filedes, MESSAGE, strlen (MESSAGE) + 1);
  37   if (nbytes < 0)
  38     {
  39       perror ("write");
  40       exit (EXIT_FAILURE);
  41     }
  42 }
  43
  44
  45 int
  46 main (void)
  47 {
  48   extern void init_sockaddr (struct sockaddr_in *name,
  49                              const char *hostname,
  50                              uint16_t port);
  51   int sock;
  52   struct sockaddr_in servername;
  53
  54   /* Create the socket.  */
  55   sock = socket (PF_INET, SOCK_STREAM, 0);
  56   if (sock < 0)
  57     {
  58       perror ("socket (client)");
  59       exit (EXIT_FAILURE);
  60     }
  61
  62   /* Connect to the server.  */
  63   init_sockaddr (&servername, SERVERHOST, PORT);
  64   if (0 > connect (sock,
  65                    (struct sockaddr *) &servername,
  66                    sizeof (servername)))
  67     {
  68       perror ("connect (client)");
  69       exit (EXIT_FAILURE);
  70     }
  71
  72   /* Send data to the server.  */
  73   write_to_server (sock);
  74   close (sock);
  75   exit (EXIT_SUCCESS);
  76 }