Connect via JavaScript SDK

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 globally 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.

MQTT.js usage example

This example contains the complete code of MQTT.js in JavaScript language connecting EMQX, 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()) })

MQTT.js MQTT 5.0 support

Currently, MQTT.js has fully supported MQTT 5.0.