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

   int
main(int argc, char *argv[])
{
    int				cnt;
    int				s_mc;
    int				rcvbuf_len;
    struct sockaddr_in		addr;
    int				addrlen;
    struct ip_mreq		mreq;

    unsigned char		buf[16];



    /*
     * INIT MULTICAST COMM
     */

    if ((s_mc = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP)) == -1)
    {
        fprintf(stderr, "client: Multicast socket() open fail. %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(25000);
    addr.sin_addr.s_addr = inet_addr("224.0.0.250");
    addrlen = sizeof(addr);

    if (bind(s_mc, (struct sockaddr *) &addr, sizeof(addr)) == -1)
    {
        fprintf(stderr, "client: Multicast bind() port fail. %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    mreq.imr_multiaddr.s_addr = inet_addr("224.0.0.250");
    mreq.imr_interface.s_addr = INADDR_ANY;

    if (setsockopt(s_mc, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) == -1)
    {
        fprintf(stderr, "client: Multicast setsockopt(IP_ADD_MEMBERSHIP) fail. %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    /* 2048 works */
    /* rcvbuf_len = 2048; */

    /* 1024 does not work */
    rcvbuf_len = 1024;
    if (setsockopt(s_mc, SOL_SOCKET, SO_RCVBUF, (const void *)&rcvbuf_len, sizeof(rcvbuf_len)) == -1)
    {
        fprintf(stderr, ": Multicast setsockopt(SO_RCVBUF) fail. %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    fprintf(stderr, "MC: START LOOP\n");

    for (;;)
    {
        if ((cnt = recvfrom(s_mc, (void *)&buf, sizeof(buf), 0, (struct sockaddr *) &addr, (socklen_t *)&addrlen)) == -1)
        {
            if (errno != EWOULDBLOCK)
            {
                fprintf(stderr, "client: Multicast recvfrom() fail. %s\n", strerror(errno));
                exit(EXIT_FAILURE);
            }
        }

        if (cnt != -1)
        {
            fprintf(stderr, "MC: %d %s\n", sizeof(buf), buf);
        }
    }
}