test.php

<?php
function sendTestRequest($id) {
    $socket = new \ZMQSocket(new \ZMQContext(), \ZMQ::SOCKET_REQ);
    $socket->connect("tcp://192.168.98.142:5668");
    $socket->send(json_encode(array("event" => 'test', "data" => $id)), \ZMQ::MODE_DONTWAIT);
    $response = $socket->recv();
    $parsedResponse = json_decode($response);
    return $parsedResponse;
  }

for ($i = 0; $i <= 10; $i++) {
  $response = sendTestRequest($i);
  echo "$i ---> $response\n";
}

zmqTest.js

var zmq = require('zmq');
var zmqResponder = zmq.socket('rep');

zmqResponder.on('message', function (msg, data) {
var parsed = JSON.parse(msg);
console.info('ZMQ Request received: ' + parsed.event);

setTimeout(function () {
  console.log('received: ' + parsed.data);
  zmqResponder.send(JSON.stringify('Message ID: ' + parsed.data));
}, (Math.floor(Math.random() * (10 - 5 + 1)) + 5) * 1000);

});

zmqResponder.bind('tcp://*:5668', function (err) {
  if (err) {
    console.error(err);
  } else {
    console.info("ZMQ awaiting orders on port 5668");
  }
});