multicast receiver

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

#define MAX_LEN  1024

int main(int argc, char *argv[])
{
	int sock;
	int flag_on = 1;
	struct sockaddr_in multicast_addr;
	char message_received[MAX_LEN+1];
	int msgrecv_len;
	struct ip_mreq mc_req;
	char* multicast_ip;
	unsigned short multicast_port;
	struct sockaddr_in from_addr;
	unsigned int from_len;
/*
	if (argc != 3)
	{
		fprintf(stderr, "Usage: %s Multicast_IP Multicast_Port\n", argv[0]);
		exit(1);
	}
*/
	multicast_ip = "224.5.6.7";//argv[1];      /* arg 1: multicast ip address */
	multicast_port = 5006;//atoi(argv[2]);    /* arg 2: multicast port number */

	if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
	{
		perror("socket() failed");
		exit(1);
	}

	/* set reuse port to on to allow multiple binds per host */
	if ((setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &flag_on,
	sizeof(flag_on))) < 0)
	{
		perror("setsockopt() failed");
		exit(1);
	}

	/* construct a multicast address structure */
	memset(&multicast_addr, 0, sizeof(multicast_addr));
	multicast_addr.sin_family      = AF_INET;
	multicast_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	multicast_addr.sin_port        = htons(multicast_port);

	/* bind to multicast address to socket */
	if ((bind(sock, (struct sockaddr *) &multicast_addr, sizeof(multicast_addr))) < 0)
	{
		perror("bind() failed");
		exit(1);
	}

	/* construct an IGMP join request structure */
	mc_req.imr_multiaddr.s_addr = inet_addr(multicast_ip);
	mc_req.imr_interface.s_addr = htonl(INADDR_ANY);

	/* send an ADD MEMBERSHIP message via setsockopt */
	if ((setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void*) &mc_req, sizeof(mc_req))) < 0)
	{
		perror("setsockopt() failed");
		exit(1);
	}

	while(1)
	{
		memset(message_received, 0, sizeof(message_received));
		from_len = sizeof(from_addr);
		memset(&from_addr, 0, from_len);

		/* block waiting to receive a packet */
		if ((msgrecv_len = recvfrom(sock, message_received, MAX_LEN, 0, (struct sockaddr*)&from_addr, &from_len)) < 0)
		{
			perror("recvfrom() failed");
			break;
		}

		printf("Received %d bytes from %s: ", msgrecv_len,
		inet_ntoa(from_addr.sin_addr));
		printf("%s", message_received);
	}

	/* send a DROP MEMBERSHIP message via setsockopt */
	if ((setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (void*) &mc_req, sizeof(mc_req))) < 0)
	{
		perror("setsockopt() failed");
		exit(1);
	}
	close(sock);
}