Is it possible write a PubSubHubBub hub service over ZeroMQ ?
UPDATE: I didn't intend rewrite PubSubHubbub protocol. I thought it was possible to write a HUB, implemented on top of ZMQ_PUB/ZMQ_SUB socket (zmq_socket(3)), but it's not clear to me until now, if it make sense or what.
PubSubHubbub has its own protocol. To make 0mq use the protocol you would have to add a new teansport to 0MQ. Which is a rather complex thing to do, especially as PubSubHubbub protocol is based on XML and thus not that easily parsable.
You can implement PubSubHubbub/0MQ bridge though. It should be easy.