[zeromq-dev] One socket per thread or per call?

Patrick Boettcher patrick.boettcher at posteo.de
Mon Jan 30 23:22:57 CET 2017

Hi all,

I'm new to zmq and still discovering things and I'd like your feedback
on a design decision.

(I asked the same question on StackOverflow, before seeing that there
is a zmq-mailing list. 

As we all know, a ZeroMQ socket shall not be shared between application
threads. Contexts however can.

I have a multi-threaded-application and I'd like to have each thread
exchange messages from time to time with a REP-socket (event, exceptions
and the like) depending what they are doing (they are doing

To send messages to my REP-socket I use the following function
(half-C++ half-pseudo-code):

  bool sendMessage(std::string s)
      zmq::socket_t socket(globalContext(), ZMQ_REQ);

      zmq::message_t message(s.size());
      memcpy(message.data(), s.data(), s.size());
      if (!socket.send(message))
          return false;

      // poll on socket for POLLIN with timeout

      // do something with message

      return true;

This function is called from every thread when needed. It creates a
local socket, connects, sends the message, and receives a response.
At exit, the socket is disconnected and removed (at least I'm
assuming that it is closed).

This way, I don't need to bother to maintain a socket in each of my
threads. This comes at the cost of creating and connecting each time I
call this function.

I stressed this code and I don't see much difference between reusing
one socket and this reconnect-implementation. (I have 20k REP-REQ per
second, including json-decode/encode, in both cases)

Is there a more correct ZeroMQ-way of doing this?

best regards,

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