I've got some embedded devices on my LAN that I'm working with and I'm
not sure what their netmask will be, but I know they will respond to a
particular UDP packet, so I'd like to send that UDP packet to
255.255.255.255, but that doesn't appear to be working. If I send to my
broadcast address 10.0.0.255, then I see the packet leave my machine
with tcpdump, however the full broadcast address doesn't work.

Yes, I've set SO_BROADCAST for the socket.

Any ideas?

-- 
Jon Schewe | http://mtu.net/~jpschewe
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For I am convinced that neither death nor life, neither angels nor
demons, neither the present nor the future, nor any powers,
neither height nor depth, nor anything else in all creation, will
be able to separate us from the love of God that is in Christ
Jesus our Lord. - Romans 8:38-39