title: receiving multicast on a server with multiple interfaces (linux)
body: <p>To receive a multicast on my not default NIC (dvb) I do the following:</p>
  
  <ul>
  <li>open a socket (AF_INET, SOCK_DGRAM)</li>
  <li>join the multicast address with IP_ADD_MEMBERSHIP on the dvb interface</li>
  <li>bind the multicast address (note that a common error is to bind "0.0.0.0" and then receive on that socket even multicast you are not interested in) and the port</li>
  </ul>
  
  <p>at this point the only way to receive the needed multicast packets is to add in the routing table a rule to reach the network where the sender is (another network) trough the dvb, as if the dvb needs to reply to the multicast sender; let say a sort of source sender multicast mode. Anyone knows what is going on? The problem is annoying to me because in principle I don't know the ip of sender.</p>