Connect with JavaScript

Below is an example using MQTT.js with the TOKEN authentication mode configured on a broker. The example assumes you have Node.js v16 or higher installed on your system.

Make sure to set the following environmental variables before running the example:

BROKER_URI (e.g. mqtts://YOUR-BROKER.YOUR-NAMESPACE.cloudflarepubsub.com)
BROKER_TOKEN with a valid auth token
BROKER_TOPIC to publish to - for example, hello/world

Before running the example, make sure to install the MQTT library:


# Pre-requisite: install MQTT.jsnpm install mqtt --save

Copy the following example as example.js and run it with node example.js.


const mqtt = require("mqtt");

// Specify MQTT broker URI: mqtts://<broker name>.<namespace>.cloudflarepubsub.com
const uri = check_env(process.env.BROKER_URI);

// Any username and your token from the /brokers/YOUR_BROKER/credentials endpoint
// The token should be the base64-encoded JWT issued by the Pub/Sub API
const username = "anything";
const password = check_env(process.env.BROKER_TOKEN);

// Specify a topic name to subscribe to and publish on
let topic = check_env(process.env.BROKER_TOPIC);

// Configure and create the MQTT client
const client = mqtt.connect(uri, {  protocolVersion: 5,  port: 8883,  clean: true,  connectTimeout: 2000, // 2 seconds  clientId: "",  username,  password,
});

// Emit errors and exitclient.on("error", function (err) {  console.log(`⚠️  error: ${err}`);  client.end();  process.exit();
});

// Connect to your brokerclient.on("connect", function () {  console.log(`🌎 connected to ${process.env.BROKER_URI}!`);  // Subscribe to a topic  client.subscribe(topic, function (err) {    if (!err) {      console.log(`✅ subscribed to ${topic}`);      // Publish a message!      client.publish(topic, "My first MQTT message");    }  });
});

// Start waiting for messagesclient.on("message", async function (topic, message) {  console.log(`received a message: ${message.toString()}`);
  // Goodbye!  client.end();  process.exit();
});

// Return variable or throw error
function check_env(env) {  if (!env) {    throw "BROKER_URI, BROKER_TOKEN and BROKER_TOPIC must be set.";  }
  return env;
}