Problem receiving UDP broadcast packets.

Thomas Heller theller at
Wed Apr 20 06:18:04 EDT 2011

Am 20.04.2011 00:21, schrieb Grant Edwards:
> I'm have problems figuring out how to receive UDP broadcast packets on
> Linux.
> On the receiving machine, I've used tcpdump to verify that broadcast
> packets are being seen and have a destination IP of and
> destination MAC of ff:ff:ff:ff:ff:ff
> But, the receiving Python program never sees any packets unless the
> _source_ IP address in the packets is on the same subnet as the
> receiving machine.  In this test case, the receiving machine has an IP
> address of  If I change the receiving machine's IP
> address to, then the receiving program sees the packets.
> Even though the destination address is, the receiving
> machine appears to discard the packets based on the _source_ IP.  Can
> anybody provide example Python code for Linux that receives UDP
> broadcast packets regardless of their source IP address?
> This probably is more of a Linux networking question than a Python
> question, but I'm hoping somebody has solved this problem in Python.

You must set the network interface to promiscous mode on the receiving side:

os.system("ifconfig eth0 promisc")


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