[clug] broadcast multicast networking

Hugh Fisher hugh.fisher at anu.edu.au
Wed Jan 10 01:38:47 GMT 2007

Adrian Blake wrote:
> I am seeking some direction on the best approach.
> I need to send short packets, under 10 bytes, to 96 devices every 
> second. If the packet is not received it is not important because the 
> next will have the new data. The data does not vary much between 
> successive packets. All devices are on the same network.
> What is the best way to achieve this? UDP packets to the broadcast address.

Broadcasting is evil - generates work for every interface on
the subnet even if they're completely uninterested in what
you're sending. (It would be OK if the 96 devices are the
only devices on the network.)

I suggest picking a multicast address in the 239.x.x.x range
and sending UDP packets to that. If you want to be dynamic
and cooperative about it, use ZeroConf AKA Rendezvous AKA
Bonjour to obtain the address, otherwise just make one up.


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