mqtt-test.js

var mqtt = require('mqtt')
var client = mqtt.connect('mqtt://127.0.0.1')

client.on('connect', function () {
  client.subscribe('presence')
  client.publish('presence', 'Hello mqtt')
})

client.on('message', function (topic, message) {
  // message is Buffer
  console.log(message.toString())
  client.end()
})

mqtt-server.js

var mosca = require('mosca')

var settings = {
  port: 1883,
  backend: {},
}

var server = new mosca.Server(settings)

server.on('clientConnected', function (client) {
  console.log('client connected', client.id)
})

server.on('published', function (packet, client) {
  console.log('Published', packet.payload)
})

server.on('ready', setup)

function setup() {
  console.log('Mosca server is up and running')
}

package.json

{
  "name": "mqtt-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "mosca": "^2.8.3",
    "mqtt": "^3.0.0"
  }
}