UDP broadcasting

Hi, I’m trying to get a basic IP-based network running between 2 or 3
and I’m having trouble trying to send broadcast UDP packets via
dial_tone_sink.py in the network examples. I’m sending the packets
addressed to with port 0 but this continuously results
in a
“can’t open socket” error. If I address the packets directly to another
machine, it works fine. Is there something else I need
to do
to broadcast packets?