[lwip-devel] Multicast Addressing

[Bill Florac]

I'm having a problem with sending a UDP message using the same multicast address/port for receiving and sending.

I set up the connection as:
  udp_bind(slp_pcb, &slpmcast, SLP_RESERVED_PORT);      // sets up local_ip, local_port
  udp_connect(slp_pcb, &slpmcast, SLP_RESERVED_PORT);   // sets up remote_ip, remote_port
  udp_recv(slp_pcb, slp_recv, 0);

However this does not work as expected.

When receiving, since this is a connected pcb, the function udp_input() check the remote_ip to the packet source and bails if they don't match.

When sending, the function udp_send() checks the local_ip to the interface->ip_addr and bails if they don't match.

I have easy fixes for both cases that I can provide but before I go into details, perhaps I'm just setting this up wrong? I can also work around it by not using udp_connet and sending packets with udp_sendto() but it seems the original should work.

Bill Florac