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

#define TEST_PORT 12345
#define BUFSIZE 512
#define USAGE_STMT "Usage: argv[0] <address>\n"

int main(int argc, char* argv[])
{
	int i, s, duh;
	struct sockaddr_in saddr;
	char buf[BUFSIZE];
	struct ip_mreq mreq;

	if (argc != 2)
	{
		printf(USAGE_STMT);
		return -1;
	}

	if((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
	{
		printf("argv[0]: cannot get socket descriptor\n");
		return -1;
	}
	
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons(TEST_PORT);
	saddr.sin_addr.s_addr = htonl(INADDR_ANY);
	
	if(bind(s, &saddr, sizeof(struct sockaddr_in)) == -1)
	{
		printf("%s: could not name socket\n", argv[0]);
		return -1;
	}

	if(inet_aton(argv[1], &(mreq.imr_multiaddr)) == 0)
	{
		printf("You have specified an invalid address to join.\n");
		return -1;
	}
	if(inet_aton("192.168.1.7", &(mreq.imr_interface)) == 0)
	{
		printf("You have specified an invalid interface address.\n");
		return -1;
	}
	
	setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(struct ip_mreq));
	memset(&saddr, 0, sizeof(struct sockaddr_in));
	duh = sizeof(struct sockaddr_in);
	
	while (recvfrom(s, buf, BUFSIZE, 0, &saddr, &duh) > 0)
	{
		printf("%s says: %s\n", inet_ntoa(saddr.sin_addr.s_addr), buf);
		memset(&saddr, 0, sizeof(struct sockaddr_in));	
	}
}