MQTT.js

Introduction

MQTT.js is a server library for the MQTT protocol, written in node.js.

The idea of this project is to allow many different breeds of publish/subscribe, rather than the straight topic hierarchies that basic MQTT provides.

Some (sane) examples:

• Subscribing to regular expressions and receiving messages on topics matching that regular expression
• CouchDB query style subscriptions
• Content based publish/subscribe using regular expressions
• Subscriptions using AWK scripts

Some (less sane) examples:

• Publishers publish image data which is processed for face detection. Subscribers subscribe to a face and get delivered the published image data if their face appears in the image
• Publishers publish MP3s. The published message is processed to determine the musical key of the published audio. Subscribers subscribe to a given musical key and receive the audio if the published audio is in that key.

How to get something useful up and running

1. Install node

2. Get MQTT.js

   git clone http://github.com/adamvr/MQTT.js.git

3. cd MQTT.js/examples

4. Run an example server using

   node <server>.js

Library usage example

MQTTServer = require("./mqtt").MQTTServer
s = new MQTTServer();
s.on('new_client', function(client) {
client.on('connect', function(packet) {
    client.connack(0);
});

client.on('publish', function(packet) {
    client.publish(packet.topic, packet.payload);
});

client.on('subscribe', function(packet) {
    // See examples
    client.suback(packet.messageId, []);
});

client.on('disconnect', function(packet) {
    // Goodbye!
});

client.on('error', function(error) {
    // Error!
});
});

s.server.listen(1883);

Caveats

At this point, MQTT.js is fairly flakey and still has some unresolved problems. Some known ones are:

• Poor handling (i.e. crashing) if partial packets are received.
• Poor handling of socket errors.
• Lack of documentation.
• Not quite as nice an API as you might like.
• Not nearly as catchy a name as mosquitto.