client.js

require('dotenv').config();
const mqtt = require('mqtt');

(async () => {
  if (!process.env.MOSQUITTO_SERVER) {
    throw Error('You should first fill the .env-example file and rename it to .env');
  }

  let client;

  // Connect to the MQTT server
  console.log('Connecting...');
  client = await mqtt.connectAsync(
    // Note: you can replace 'mqtts' per 'wss' to connect to Mosquitto using websockets (you need to activate the option on Stackhero console and to configure "Security shield" to allow your IPs).
    `mqtts://${process.env.MOSQUITTO_SERVER}:${process.env.MOSQUITTO_PORT}`,
    {
      username: process.env.MOSQUITTO_USERNAME,
      password: process.env.MOSQUITTO_PASSWORD,
      clean: true
    }
  );
  console.log('Connected');


  // This callback will be executed when a message is received on topics you subscribed (see client.subscribe below).
  client.on(
    'message',
    (topic, message) => console.log(`Message received on topic "${topic}": ${message.toString()}`)
  );


  // Subscribe to the topic "global"
  console.log('Subscribing to "global" topic...');
  await client.subscribeAsync('global');
  console.log('Subscribed to "global" topic');


  // Publish to the topic "global"
  console.log('Publishing to "global" topic...');
  await client.publishAsync(
    'global',
    'Hello everyone!',
    { qos: 2 }
  );
  console.log('Published to "global" topic');


  // Publish to a user topic
  console.log('Publishing to "users/testUser/sensor1" topic...');
  await client.publishAsync(
    'users/testUser/sensor1',
    '123',
    { qos: 2 }
  );
  console.log('Published to "users/testUser/sensor1" topic');

  // Note: we can publish to a topic without "write" rights. MQTT will ignore the message without informing us.
})().catch(error => {
  console.error('');
  console.error('🐞 An error occurred!');
  console.error(error);
  process.exit(1);
});