[zeromq-dev] thread safety using inproc sockets for inter-thread communication

[Bill Torpey]

Hi All:

I don’t see this addressed specifically in the docs, in the GitHub issues, or here, so thought I’d ask.

I bind an inproc sub socket for inter-thread communication, which I include in zmq_poll.  When I want to e.g., subscribe from a different thread I create a pub socket, connect to the first and send it a command message, which then gets executed on the main zmq thread.  So far, so good.

What I’m wondering if it’s OK to immediately disconnect the socket after calling zmq_send, like so:

   void* temp = zmq_socket(impl->mZmqContext, ZMQ_PUB);
   zmq_connect(temp, ZMQ_CONTROL_ENDPOINT);
   zmq_pollitem_t pollitems [] = { { temp, 0, ZMQ_POLLIN, 0 } };
   CALL_ZMQ_FUNC(zmq_poll(pollitems, 1, 1));				// see https://github.com/zeromq/libzmq/issues/2267
   zmq_send(temp, msg, msgSize, 0);
   zmq_disconnect(temp, ZMQ_CONTROL_ENDPOINT);
   zmq_close(temp);

This *seems* to work, but I’m concerned that maybe I’m just getting "lucky”?  It does *not* appear to work with ZMQ_PAIR sockets, for whatever reason, although I’ve seen that approach recommended in a few places. 

Thanks in advance for any assistance!

Regards,

Bill Torpey