DAWN/src/network/multicastsocket.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#include "multicastsocket.h"

static struct ip_mreq command; /* static ?! */

int setup_multicast_socket(const char *_multicast_ip, unsigned short _multicast_port, struct sockaddr_in *addr)
{
  int loop = 1;
  int sock;

  memset (addr, 0, sizeof (*addr));
  addr->sin_family = AF_INET;
  addr->sin_addr.s_addr = htonl (INADDR_ANY);
  addr->sin_port = htons (_multicast_port);

  if ( ( sock = socket(PF_INET, SOCK_DGRAM, 0)) == -1) {
     perror ("socket()");
     exit (EXIT_FAILURE);
  }

  /* Mehr Prozessen erlauben, denselben Port zu nutzen */
  loop = 1;
  if (setsockopt ( sock,
                   SOL_SOCKET,
                   SO_REUSEADDR,
                   &loop, sizeof (loop)) < 0) {
     perror ("setsockopt:SO_REUSEADDR");
     exit (EXIT_FAILURE);
  }
  if(bind( sock,
           (struct sockaddr *)addr,
           sizeof(*addr)) < 0) {
     perror ("bind");
     exit (EXIT_FAILURE);
  }

  /* Broadcast auf dieser Maschine zulassen */
  loop = 1;
  if (setsockopt ( sock,
                   IPPROTO_IP,
                   IP_MULTICAST_LOOP,
                   &loop, sizeof (loop)) < 0) {
     perror ("setsockopt:IP_MULTICAST_LOOP");
     exit (EXIT_FAILURE);
  }

  /* Join the broadcast group: */
  command.imr_multiaddr.s_addr = inet_addr (_multicast_ip);
  command.imr_interface.s_addr = htonl (INADDR_ANY);
  if (command.imr_multiaddr.s_addr == -1) {
     perror ("224.0.0.1 ist keine Multicast-Adresse\n");
     exit (EXIT_FAILURE);
  }
  if (setsockopt ( sock,
                   IPPROTO_IP,
                   IP_ADD_MEMBERSHIP,
                   &command, sizeof (command)) < 0) {
    perror ("setsockopt:IP_ADD_MEMBERSHIP");
  }
  return sock;
}