How to set up a socket for UDP multicast with 2 network cards present?

Question

I\'m trying to get udp multicast data using sockets and c++ (c). I have a server with 2 network cards so I need to bind socket to specific interface. Currently I\'m testing

Answer 1

I think you need to add IP_MULTICAST_IF

    struct  ip_mreq         multi;

   multi.imr_multiaddr.s_addr = inet_addr(group.c_str());
   multi.imr_interface.s_addr = (source_iface.empty() ?
         htonl(INADDR_ANY): inet_addr(source_iface.c_str()));

    status = setsockopt(me->ns_fd, IPPROTO_IP, IP_MULTICAST_IF,
        (char *)&multi.imr_interface.s_addr,
        sizeof(multi.imr_interface.s_addr));

I hope that helps.