receiver.c

/*
 * listener.c -- joins a multicast group and echoes all data it receives from
 *		the group to its stdout...
 *
 * Antony Courtney,	25/11/94
 * Modified by: Frédéric Bastien (25/03/04)
 * to compile without warning and work correctly
 */

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

#define HELLO_PORT 23932
#define HELLO_GROUP "239.255.199.34"
#define MSGBUFSIZE 256

int main()
{
  struct sockaddr_in addr;
  int fd, nbytes;
  socklen_t addrlen;
  struct ip_mreq mreq;
  char msgbuf[MSGBUFSIZE];
  
  u_int yes=1;            /*** MODIFICATION TO ORIGINAL */
  
  /* create what looks like an ordinary UDP socket */
  if ((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0) {
    perror("socket");
    exit(1);
  }
  
  
  /**** MODIFICATION TO ORIGINAL */
  /* allow multiple sockets to use the same PORT number */
  if (setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(yes)) < 0) {
    perror("Reusing ADDR failed");
    exit(1);
  }
  /*** END OF MODIFICATION TO ORIGINAL */
  
  /* set up destination address */
  memset(&addr,0,sizeof(addr));
  addr.sin_family=AF_INET;
  addr.sin_addr.s_addr=htonl(INADDR_ANY); /* N.B.: differs from sender */
  addr.sin_port=htons(HELLO_PORT);
  
  /* bind to receive address */
  if (bind(fd,(struct sockaddr *) &addr,sizeof(addr)) < 0) {
    perror("bind");
    exit(1);
  }
  
  /* use setsockopt() to request that the kernel join a multicast group */
  mreq.imr_multiaddr.s_addr=inet_addr(HELLO_GROUP);
  mreq.imr_interface.s_addr=htonl(INADDR_ANY);
  if (setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq)) < 0) {
    perror("setsockopt");
    exit(1);
  }
  
  /* now just enter a read-print loop */
  while (1) {
    addrlen=sizeof(addr);
    if ((nbytes=recvfrom(fd,msgbuf,MSGBUFSIZE,0,
			 (struct sockaddr *) &addr, &addrlen)) < 0) {
      perror("recvfrom");
      exit(1);
    }
    printf("%s", msgbuf);
  }
}