How I can receive UDP multicast from all subnets?

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. */

user207421 · Answer 1 · 2013-07-12T12:16:49.357

0

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.

edited Jul 12 '13 at 12:16

answered Jul 12 '13 at 10:11

user207421

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I have only one interface eth0 (and lo). – AndreyKeen Jul 12 '13 at 10:15
In that case you need to look at your router configuration. It isn't configured to pass multicast through. – user207421 Jul 12 '13 at 11:03
But tcpdump on my computer (192.168.3.2) catched multicast from network 192.168.1.0/24. – AndreyKeen Jul 12 '13 at 11:38
So what subnet didn't you receive multicasts from? – user207421 Jul 19 '13 at 22:55
Instead for 9 line: `localSock.sin_addr.s_addr = INADDR_ANY;` This code receive multicast only 192.168.3.0/24 net. But tcpdump catched multicast from all subnets. – AndreyKeen Jul 24 '13 at 11:49
I solved a problem. It was necessary to use an `recvfrom()` and I used `read()`. – AndreyKeen Jul 25 '13 at 11:35

How I can receive UDP multicast from all subnets?

1 Answers1