sockets - How does zmq poller work? -

i confused poller in zmq. zguide goes minimally, , describes way read multiple sockets. not satisfying answer me because not explain how have timeout sockets. know zeromq: how prevent infinite wait? explains push/pull, not req/rep patterns, want know how use.

what attempting ask is: how poller work, , how function apply keeping track of sockets , requests?

when need listen on different sockets in same thread, use poller:

zmq.socket subscriber = ctx.socket(zmq.sub) zmq.socket puller = ctx.socket(zmq.pull) 

register sockets poller (pollin listens incoming messages)

zmq.poller poller = zmq.poller(2) poller.register(subscriber, zmq.poller.pollin) poller.register(puller, zmq.poller.pollin) 

when polling, use loop:

while( notinterrupted()){   poller.poll()    //subscriber registered @ index '0'   if( poller.pollin(0))       subscriber.recv(zmq.dontwait)    //puller registered @ index '1'   if( poller.pollin(1))      puller.recv( zmq.dontwait) } 

choose how want poll...

poller.poll() blocks until there's data on either socket.
poller.poll(1000) blocks 1s, times out.

the poller notifies when there's data (messages) available on sockets; it's job read it.

when reading, without blocking: socket.recv( zmq.dontwait). though poller.pollin(0) checks if there's data read, want avoid blocking calls inside polling loop, otherwise, end blocking poller due 'stuck' socket.

so, if 2 separate messages sent subscriber, have invoke subscriber.recv() twice in order clear poller, otherwise, if call subscriber.recv() once, poller keep telling there's message read. so, in essence, poller tracks availability , number of messages, not actual messages.

you should run through polling examples , play code, it's best way learn.

does answer question?