Hi Martin: This is just a guess, but it’s an educated guess. The doc for zmq_socket_monitor says:
> Each call to this method creates a ZMQ_PAIR socket and binds that to the > specified inproc:// endpoint. The newly-created socket doesn’t have any connections until you connect to it. (You probably also want to delete the old socket and create a new one to connect to the monitor endpoint). I haven’t tested this, but based on what I’ve seen from zmq_socket_monitor this seems worth a try. Regards, Bill P.S. The blocking behavior on the second connect makes sense also: be careful when using socket monitoring — if you don’t consume monitor events, subsequent operations on the sockets you are monitoring will block. > On Oct 31, 2018, at 3:26 PM, <martin.belan...@dell.com> > <martin.belan...@dell.com> wrote: > > I want to be able to turn on/off monitoring using zmq_socket_monitor(). > > I turn on monitoring as follows: > zmq_socket_monitor(sock_to_monitor_p, "inproc://monitor-my-sock", > ZMQ_EVENT_ALL) > > And I turn it off this way: > zmq_socket_monitor(sock_to_monitor_p, NULL, 0) > > I designed my main process to be configurable. I send messages to it to tell > it to turn monitoring on/off in real time. > > The first time I turn on monitoring, everything works as expected, i.e. the > monitor thread starts receiving events. > When I turn off monitoring, again everything works fine, events are no longer > received. > When I try to turn on monitoring again, nothing happens. The monitor thread > doesn't receive events. > When I try to turn on monitoring yet again, the API zmq_socket_monitor() just > blocks (doesn't return). > > Any idea why this is happening? > > I looked at function zmq::socket_base_t::monitor() and I can't see anything > wrong with it. I see that this function will close the monitor socket when > endpoint_=NULL. And it will create a new monitor socket when endpoint_ is not > NULL. That function was clearly designed to allow switching monitoring on/off > as often as we like. So not sure what is going on here. > > By the way, it would be nice if there was a separate API to allow changing > the event mask without having to close and open the monitor socket. This way > I could change the events back and forth between 0 and ZMQ_EVENT_ALL. That > would achieve what I'm trying to do with minimal impact (i.e. no socket > closing and re-opening). > > Regards, > Martin > _______________________________________________ > zeromq-dev mailing list > zeromq-dev@lists.zeromq.org > https://lists.zeromq.org/mailman/listinfo/zeromq-dev
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