PUB/SUB for respective process on ZeroMQ example.

pub.cpp

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <assert.h>

#include <unistd.h>

#include <zmq.hpp>

const int max_peer = 3;

int main() {
  zmq::context_t context(1);
  zmq::socket_t sock(context,ZMQ_PUB);
  sock.bind("ipc:///test1");

  while (1) {
    sleep(1);

    char buf[256];
    int len;

    int peer = rand()%max_peer;
    len = sprintf(buf,"%d ",peer);
    sock.send(buf,len,ZMQ_SNDMORE);

    len = sprintf(buf,"%d ",rand());
    sock.send(buf,len,0);
  }
}

sub.cpp

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <assert.h>

#include <unistd.h>

#include <zmq.hpp>

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

  if (argc<2) return 0;
  int peer_id = atoi(argv[1]);

  printf("peer_id=%d\n",peer_id);

  zmq::context_t context(1);
  zmq::socket_t sock(context,ZMQ_SUB);
  sock.connect("ipc:///test1");

  char buf[256];
  int len = sprintf(buf,"%d ",peer_id);
  sock.setsockopt(ZMQ_SUBSCRIBE,buf,len);

  while (1) {
    zmq::message_t msg;
    sock.recv(&msg);
    memcpy(buf,msg.data(),msg.size());
    buf[msg.size()]=0;
    puts(buf);
  }
}