[zeromq-dev] Fwd: Inverted PUB-SUB doesn't work

[Rajalakshmi Iyer]

Hello,

I have a use case where multiple publishers need to send messages to a
single subscriber. I have tried implementing the inverted PUB-SUB pattern
as follows -

#include <zmq.hpp>
#include <iostream>

int main()
{
   try
   {
      int major, minor, patch;
      zmq_version(&major, &minor, &patch);
      std::cout << "ZeroMQ version " << major << "." << minor << "." <<
patch << " " << std::endl;

      zmq::context_t ctx(1);
      zmq::socket_t sender(ctx, ZMQ_PUB);
      zmq::socket_t receiver(ctx, ZMQ_SUB);


      receiver.bind("tcp://127.0.0.1:5557");
      std::cout << "Subscriber bind" << std::endl;

      sender.connect("tcp://127.0.0.1:5557");
      std::cout << "Publisher connect" << std::endl;

      zmq::message_t sendMsg;
      memcpy(sendMsg.data(), (char*)("Hello!"), 6);
      sender.send(sendMsg);
      std::cout << "Publisher send" << std::endl;

      zmq::message_t recvMsg;
      receiver.recv(&recvMsg);
      std::string message = std::string(static_cast<char*>(recvMsg.data()),
recvMsg.size());
      std::cout << "Subscriber recv: " << message << std::endl;

   } catch (zmq::error_t err)
   {
      std::cout << "Error : " << err.what() << std::endl;
   }
}

The output of this is -
ZeroMQ version 4.0.4
Subscriber bind
Publisher connect
Publisher send

As can be seen, the subscriber is unable to receive the message sent by the
publisher and the recv() call blocks.

Any ideas on what might be going wrong would be useful.

Thanks!

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