MQTT JavaScript Client Library

MQTT.js is a module written in JavaScript that implements the MQTT protocol client function and can be used in browsers and Node.js environments.

Due to the single-threaded nature of JavaScript, MQTT.js is a fully asynchronous MQTT client. MQTT.js supports MQTT and MQTT over WebSocket. The support in different operating environments is as follows:

• Browser environment: MQTT over WebSocket (including WeChat applet, Alipay applet and other customized browser environments)
• Node.js environment: MQTT, MQTT over WebSocket

Except for a small number of connection parameters that is different in different environments, the other APIs are the same.

Install using npm :

npm i mqtt

Install using CDN (browser):

<script src="https://unpkg.com/mqtt/dist/mqtt.min.js"></script>
<script>
    // Initialize a mqtt variable globally
    console.log(mqtt)
</script>

In the environment where Node.js is installed, you can use MQTT.js global ly in the form of a command line of npm i mqtt -g command.

npm i mqtt -g

mqtt help

> MQTT.js command line interface, available commands are:

  * publish     publish a message to the broker
  * subscribe   subscribe for updates from the broker
  * version     the current MQTT.js version
  * help        help about commands

> Launch 'mqtt help [command]' to know more about the commands.

TIP

Currently, MQTT.js has fully supported MQTT 5.0.

Quick Start Tutorial

This example contains the complete code of MQTT.js in JavaScrip language connecting EMQX Broker, sending and receiving messages:

// const mqtt = require('mqtt')
import mqtt from 'mqtt'

// connection option
const options = {
  		clean: true, // retain session
      connectTimeout: 4000, // Timeout period
      // Authentication information
      clientId: 'emqx_test',
      username: 'emqx_test',
      password: 'emqx_test',
}

// Connect string, and specify the connection method by the protocol
// ws Unencrypted WebSocket connection
// wss Encrypted WebSocket connection
// mqtt Unencrypted TCP connection
// mqtts Encrypted TCP connection
// wxs WeChat applet connection
// alis Alipay applet connection
const connectUrl = 'wss://broker.emqx.io:8084/mqtt'
const client = mqtt.connect(connectUrl, options)

client.on('reconnect', (error) => {
    console.log('reconnecting:', error)
})

client.on('error', (error) => {
    console.log('Connection failed:', error)
})

client.on('message', (topic, message) => {
  console.log('receive message：', topic, message.toString())
})