MQTT Service Singleton

MQTT Service Singleton

var mqtt    = require('mqtt');
var uuid = require('node-uuid');

// Import events module
var events = require('events');

var MQTTService = (function () {
  var instance;
  function init() {
    const NOTIFICATION_MESSAGE = 'F9D4494D-62F8-4CBD-BCCA-CC3DB557276A'
    const SYSTEM_MESSAGE       = '0F9AEAF1-EF9C-4414-9C1C-959B2EFC41EF';
    const MQTT_SERVER = 'mqtt://54.249.44.123';

    var mqttOptions = {
      port:1883,
      username:'appuser',
      password:'iloveapp',
      clientId: 'serverjs_'+uuid.v1(),
      clear:false
    }
    var eventEmitter = new events.EventEmitter();
    var MessageClient  = mqtt.connect(MQTT_SERVER,mqttOptions);

    MessageClient.on('connect', function () {
      MessageClient.subscribe(SYSTEM_MESSAGE);
    });

    MessageClient.on('message', function (topic, message) {
      console.log(topic+'---'+message);
      eventEmitter.emit(topic,message);
    });

    //Public Method
    return {
      NOTIFICATION_MESSAGE:NOTIFICATION_MESSAGE,
      SYSTEM_MESSAGE:SYSTEM_MESSAGE,
      
      publishMessage : function(topic,msg) {
        MessageClient.publish(topic,msg);
      },
      listenTo : function(topic,lscb) {
        console.log('add');
        eventEmitter.on(topic, lscb);
      }
    };

  };

  return {
    getInstance: function () {

      if ( !instance ) {
        instance = init();
      }
      return instance;
    }

  };

})();

module.exports = MQTTService;

//How to use it.
var mqttService = require('../../common/models/mqttService.js');

var myMQTT = mqttService.getInstance();

  console.log(myMQTT.SYSTEM_MESSAGE);
  myMQTT.listenTo(myMQTT.SYSTEM_MESSAGE,function(message){
    console.log('MQTT:'+message.toString());
  })