ØMQ came to mind when I read the doc, too, but:

* UDP could be useful for hole-punching firewalls * In most networks, multicast traffic will be filtered at the WAN boundary * The nodes in most big DHTs aren't reliable anyway

The eventing would be nice, though... and the notion of an internet-wide ØMQ network is neat.

0mq is a library to make network programming easier, not a new protocol itself.

UDP is being used because this is based on setting up a DHT which requires small messages that may or may not get through by nature to begin with - not bulk data transfer - presumably you deal with that at higher layers.

0mq is an extension of the standard socket library and does support a reliable multicast protocol. It adds to sockets, its not just an api to make working with the existing standards easier.

http://manpages.ubuntu.com/manpages/maverick/man7/zmq_pgm.7....

Though, it looks like it might need more permissions than just using standard sockets.

Seems like an interesting idea. I also wonder why the max contents of a JSON object is 1400 bytes, that seems kind of limiting. UDP can do 65,507b of content...

The bigger an UDP packet the less the probability it arrives. 1400 is probably chosen because it is less than the usual MTU of ethernet which is 1500.