[Discuss-gnuradio] UDP broadcasting

Hi, I'm trying to get a basic IP-based network running between 2 or 3 USRPs 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 192.168.200.255 with port 0 but this continuously results in a "can't open socket" error.  If I address the packets directly to another machine 192.168.200.30, it works fine.  Is there something else I need to do to broadcast packets?