MQTT Client Library Encyclopedia – MQTT.js

Guest post by Matteo Collina

MQTT.js
LanguageJavascript
Websitehttps://github.com/mqttjs/MQTT.js
API-StyleAsynchronous, Callbacks, Streams, Offline
License MIT

Description

The MQTT.js provides a full-featured Javascript library for the MQTT protocol. It is fully isomorphic, which means it can run in the browser and in node.js (>= 0.8), including Intel Edison and Raspberry PIs. In fact, it is bundled in base image of the Intel Edison.
The library was originally written by Adam Rudd in May 2011, and it has been upgraded to all versions of node.js since then. In 2014, Matteo Collina took over as a maintainer, and since version 1.0.0 it supports MQTT over Websockets, both in Node.js and in the Browser.
This library is production ready and used by some fortune 500 companies. It can support long running clients with spotty connectivity. It has an optional on-disk storage for local offline messaging.
MQTT.js became Open Open Source last January, and it had 55 contributors in its history. There is a team of 4 that maintains the library.

Features

MQTT 3.1ok
MQTT 3.1.1ok
LWTok
SSL/TLSok
Automatic Reconnectok
QoS 0ok
QoS 1ok
QoS 2ok
Authenticationok
ThrottlingLimited

Usage

Installation

You need node.js installed to use MQTT.js, then:

If you want to use the embedded CLI tools, you need to

Connect

Connects to the broker specified by the given url and options and returns a Client.

The URL can be on the following protocols: 'mqtt', 'mqtts', 'tcp', 'tls', 'ws', 'wss'. The URL can also be an object as returned by URL.parse(), in that case the two objects are merged, i.e. you can pass a single object with both the URL and the connect options.

You can also specify a servers options with content: [{ host: 'localhost', port: 1883 }, ... ], in that case that array is iterated at every connect.

Connect with MQTT 3.1 or MQTT 3.1.1

The library connects with MQTT 3.1.1 by default. To connect with MQTT 3.1

Connect with LWT

LWT can be set in the connect function, like the following:

Connect with Username / Password

Username and password can be set in the connect function, like the following:

Publish

Publish a message to a topic

  • topic is the topic to publish to, String
  • message is the message to publish, Buffer or String
  • options are the options to publish with, including:
    • qos QoS level, Number, default 0
    • retain retain flag, Boolean, default false
  • callback callback fired when the QoS handling completes, or at the next tick if QoS 0.

Subscribe

Subscribe to a topic or topics

  • topic is a String topic to subscribe to or an Array of topics to subscribe to. It can also be an object, the object key is the topic name and the value is the QoS, like {'test1': 0, 'test2': 1}.
  • options is the options to subscribe with, including:
    • qos qos subscription level, default 0
  • callbackfunction(err, granted) callback fired on suback where:
    • err is a subscription error
    • granted is an array of {topic, qos} where:
      • topic is a subscribed to topic
      • qos is the granted qos level on it

Unsubscribe

Unsubscribe from a topic or topics

topic is a String topic or an array of topics to unsubscribe from
callback fired on unsuback

Disconnect

Using SSL / TLS

The user should call mqtt.connect(), here is a full example:

Author Information

mateo
Matteo Collina
Matteo is a code pirate and mad scientist. He spends most of his days programming in node.js, but in the past he worked with Ruby, Java and Objective-C. He recently got a Ph.D. with a thesis titled “Application Platforms for the Internet of Things”. Now he is a Software Architect at nearForm, where he consults for the top brands in world. Matteo is also the author of the Node.js MQTT Broker, Mosca and of the LevelGraph database. Matteo spoke at several international conferences: NodeSummit, Nodeconf.eu, LXJS, Distill by Engine Yard, and JsDay to name a few. He is also co-author of the book “Javascript: Best Practices” edited by FAG, Milan. In the summer he loves sailing the Sirocco.
  Website

2 comments

  1. Saili Ghavat says:

    I am trying to connect to an mqtt broker but I get this error when I try top use require.js
    Uncaught Error: Module name “mqtt” has not been loaded yet for context: _. Use require([])

    1. Mosquitto says:

      Have you imported de mqtt module?: –> var mqtt = require(‘mqtt’);

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