ZeroMQ 3.1 REQ/REP poll revents behaviour compared with 2.1.10

TestPollingReqRepZMQ3.hx

	public function testPollingReqRepZMQ3() {
		var pollinout:Int = ZMQ.ZMQ_POLLIN() | ZMQ.ZMQ_POLLOUT();
		var ctx:ZContext;
		var req:ZMQSocket, rep:ZMQSocket;
		var poller:ZMQPoller;
		
		// ** Test tcp req/rep poller revents
		var randomPort:Int = Math.round(Math.random() * 18000) + 2000;
		ctx = new ZContext();
		req = ctx.createSocket(ZMQ_REQ);
		rep = ctx.createSocket(ZMQ_REP);
		req.bind("tcp://*:"+randomPort);
		rep.connect("tcp://localhost:"+randomPort);
		Sys.sleep(0.1);	// Allow sockets time to connect
		poller = new ZMQPoller();
		poller.registerSocket(req, pollinout);
		poller.registerSocket(rep, pollinout);
		var numSocks = poller.poll(10 * ZMQ.ZMQ_POLL_MSEC());
		trace ("tcp:"+numSocks); 	// Returns:
							// "2" in ZMQ 3.1
							// "1" in ZMQ 2.1.0
		ctx.destroy();

		// ** Test ipc req/rep poller revents
		ctx = new ZContext();
		req = ctx.createSocket(ZMQ_REQ);
		rep = ctx.createSocket(ZMQ_REP);
		req.bind("ipc://test.poller");
		rep.connect("ipc://test.poller");
		Sys.sleep(0.1);	// Allow sockets time to connect
		poller = new ZMQPoller();
		poller.registerSocket(req, pollinout);
		poller.registerSocket(rep, pollinout);
		var numSocks = poller.poll(10 * ZMQ.ZMQ_POLL_MSEC());
		trace ("ipc:"+numSocks); 	// Returns:
							// "2" in ZMQ 3.1
							// "1" in ZMQ 2.1.0
		ctx.destroy();
		
		// ** Test inproc req/rep poller revents
		ctx = new ZContext();
		req = ctx.createSocket(ZMQ_REQ);
		rep = ctx.createSocket(ZMQ_REP);
		req.bind("inproc://test.poller");
		rep.connect("inproc://test.poller");
		Sys.sleep(0.1);	// Allow sockets time to connect
		poller = new ZMQPoller();
		poller.registerSocket(req, pollinout);
		poller.registerSocket(rep, pollinout);
		var numSocks = poller.poll(10 * ZMQ.ZMQ_POLL_MSEC());
		trace ("inproc:"+numSocks); 	// Returns:
							// "1" in ZMQ 3.1
							// "1" in ZMQ 2.1.0
		ctx.destroy();
		
		assertTrue(true);
	}

This is a snippet from with a Haxe.unit.TestCase class that demonstrates the different behaviour in ZMQ 3.1 between inproc and ipc/tcp transports when testing the results of a poller.poll() on a pair of REQ/REP sockets which have been connected but no messages passed between them. I found that:

1. For tcp or icp transports, the REP socket reports it is ready for a Read (ie poller.pollin(2) is TRUE), although if you do a read on it, it returns null (no data). For inproc, it returns 1 (and only the REQ socket is flagged ready, for a write).
2. In ZMQ 2.1.10, the poller.poll() call always returns 1 (and on further examination, it is the REQ socket that is ready for a Write, which is what you would expect).