MosquittoNotes.txt

Mosquitto Notes

Overview
- "Mosquitto" is a name for the MQTT protocol.
- It supports publish and subscribe operations.

To install
- brew install mosquitto

To have the MQTT server automatically start on reboots
- ln -sfv /usr/local/opt/mosquitto/*.plist ~/Library/LaunchAgents

To initially start the MQTT server
- launchctl load ~/Library/LaunchAgents/homebrew.mxcl.mosquitto.plist
- this starts a process using /usr/local/opt/mosquitto/sbin/mosquitto

To stop the server
- launchctl stop homebrew.mxcl.mosquitto

To restart the server
- launchctl start homebrew.mxcl.mosquitto

To subscribe to topic
- mosquitto_sub -t topic/state
- no quotes are needed around the -t value

To publish a message on a topic
- open a new terminal
- mosquitto_pub -t topic/state -m "Hello World"
- no quotes are needed around the -t value

To use from Node.js or browser JavaScript
- npm install mqtt
- example code:
const mqtt = require('mqtt');
const host = 'localhost';
const port = 1883;
const client = mqtt.connect('mqtt://' + host + ':' + port);

const topic = 'foo/bar';

client.on('connect', () => {
  client.subscribe(topic);
  client.publish(topic, 'Hello from MQTT!');
});

client.on('message', (topic, message) => {
  console.log(message.toString()); // message is a Buffer
  client.end(); // don't call to continue listening
});