如何从所有子网接收UDP多播？

Question

The following code receive only UDP multicast in my subnet. How I can receive UDP multicast from all subnets?

    sd = socket(AF_INET, SOCK_DGRAM, 0);
    int reuse = 1;
    setsockopt(sd, SOL_SOCKET, SO_REUSEADDR,
            (char *) &reuse, sizeof(reuse));

    memset((char *) &localSock, 0, sizeof(localSock));
    localSock.sin_family = AF_INET;
    localSock.sin_port = htons(1900);
    localSock.sin_addr.s_addr = INADDR_BROADCAST;

    bind(sd, (struct sockaddr*) &localSock, sizeof(localSock));

    group.imr_multiaddr.s_addr = inet_addr("239.255.255.250");
    group.imr_interface.s_addr = inet_addr("192.168.3.2");

    setsockopt(sd, IPPROTO_IP, IP_ADD_MEMBERSHIP,
            (char *) &group, sizeof(group));


    /* Read from the socket. */

Answer 1

You need to join the group via all interfaces, not just 192.168.3.2.

You also need to bind your socket to INADDR_ANY, not INADDR_BROADCAST.