Publisher only sending messages in infinite loop

Question

I have the following control flow. In a for loop, I make an array of strings. I send out each row of the array (a string) to a publisher function. The publisher function then is supposed to send out the strings. I have a problem where my subscriber only receives messages, if the publisher is publishing in an infinite loop. Why can I not continuously call the publisher function and have it send data out? Why is it only working in an infinite loop?

Here is my publisher function:

    int zedMQserver(std::string output)
     {

     //std ::cout << output.c_str()<< std:: endl;




zmq::context_t context (1);
zmq::socket_t publisher (context, ZMQ_PUB);
publisher.bind("tcp://*:5556");
publisher.bind("ipc://device.ipc");                // Not usable on Windows.


    int i=1;   
    //while(1) {




    //  Send message to all subscribers

  const int SIZE = output.length();

    zmq::message_t message(SIZE+1);
    snprintf ((char *) message.data(), (SIZE+1) ,
        "%s", output.c_str());
    publisher.send(message);
   std :: cout << "sent message" << std:: endl;
//}
return 0;

Here is my subscriber function:

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



int main (int argc, char *argv[])


  {

 zmq::context_t context (1);

 //Socket to talk to server
 std::cout << "Collecting updates from device server...\n" << std::endl;
 zmq::socket_t subscriber (context, ZMQ_SUB);
 subscriber.connect("tcp://localhost:5556");
 const char *filter = (argc > 1)? argv [1]: "";  // no filter currently
 subscriber.setsockopt(ZMQ_SUBSCRIBE, filter, strlen (filter));
 //  Process 100 updates
 zmq::message_t update;

 for (int q =0 ; q<1000 ; q++) {
    subscriber.recv(&update);

    std::string output = std::string(static_cast<char*>(update.data()), update.size());


    std:: cout <<output << std:: endl;       
    }  
 return 0;







  }

Why is that when I take away the while(1) statement, I don't receive anything?

Answer 1

So it turns out that this is a classic "slow joiner problem". I made the publisher sleep a bit, and it worked.