doc/examples/udp.c

   1 /* This example code is placed in the public domain. */
   2
   3 #ifdef HAVE_CONFIG_H
   4 #include <config.h>
   5 #endif
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <sys/types.h>
  11 #include <sys/socket.h>
  12 #include <arpa/inet.h>
  13 #include <netinet/in.h>
  14 #include <unistd.h>
  15
  16 /* udp.c */
  17 int udp_connect (void);
  18 void udp_close (int sd);
  19
  20 /* Connects to the peer and returns a socket
  21  * descriptor.
  22  */
  23 extern int
  24 udp_connect (void)
  25 {
  26   const char *PORT = "5557";
  27   const char *SERVER = "127.0.0.1";
  28   int err, sd, optval;
  29   struct sockaddr_in sa;
  30
  31   /* connects to server
  32    */
  33   sd = socket (AF_INET, SOCK_DGRAM, 0);
  34
  35   memset (&sa, '\0', sizeof (sa));
  36   sa.sin_family = AF_INET;
  37   sa.sin_port = htons (atoi (PORT));
  38   inet_pton (AF_INET, SERVER, &sa.sin_addr);
  39
  40 #if defined(IP_DONTFRAG)
  41   optval = 1;
  42   setsockopt (sd, IPPROTO_IP, IP_DONTFRAG,
  43               (const void *) &optval, sizeof (optval));
  44 #elif defined(IP_MTU_DISCOVER)
  45   optval = IP_PMTUDISC_DO;
  46   setsockopt(sd, IPPROTO_IP, IP_MTU_DISCOVER,
  47              (const void*) &optval, sizeof (optval));
  48 #endif
  49
  50   err = connect (sd, (struct sockaddr *) & sa, sizeof (sa));
  51   if (err < 0)
  52     {
  53       fprintf (stderr, "Connect error\n");
  54       exit (1);
  55     }
  56
  57   return sd;
  58 }
  59
  60 /* closes the given socket descriptor.
  61  */
  62 extern void
  63 udp_close (int sd)
  64 {
  65   close (sd);
  66 }