mqtt-connect

MQTT high level framework to glue together various "middleware" to handle incoming messages.

It works for both MQTT Broker and Client.

Heavily inspired by the HTTP connect module form-factor.

Broker Example

var mosca = require('mosca')
var MQTTConnect = require('mqtt-connect')
 
var settings = {
  port: 1883,
  backend: {
    type: 'mongo',
    url: 'mongodb://localhost:27017/mqtt',
    pubsubCollection: 'ascoltatori',
    mongo: {}
  }
}
 
var server = new mosca.Server(settings);
var app = new MQTTConnect.broker(server)
 
server.on('clientConnected', function(client) {
    console.log('client connected', client.id)
})
 
app.use('/topic', function(broker, client, packet, next){
  // middleware
  console.log(packet.payload)
  next()
})
 
// fired when a message is received
server.on('published', app.stack) // fn(packet, client)
 

Client Example

var mqtt = require('mqtt')
var MQTTConnect = require('mqtt-connect')
 
var client  = mqtt.connect('mqtt://test.mosquitto.org')
 
client.on('connect', function () {
  client.subscribe('presence')
  client.publish('presence', 'Hello mqtt')
})
 
var app = new MQTTConnect.Client(client)
 
app.use(function middleware1(client, msg, next) {
  // middleware 1
  next()
})
 
app.use(function (client, msg, next) {
  // middleware 2
  console.log(msg.topic)
  console.log(msg.data) // buffer
  client.publish('boop/', 'boop')
})
 
client.on('message', app.stack) // fn(topic, msg)
 

Mount middleware

The .use() method also takes an optional path string that is matched against the beginning of the incoming request topic. This allows for basic msg routing:

app.use('/topic1', function fooMiddleware(client, msg, next) {
  // your middleware logic
  next()
})

API

app.use(fn)

Use a function on the app, where the function represents a middleware. The function will be invoked for every request in the order that app.use is called. The function is called with three arguments for the client and 4 arguments for the Broker:

// Client
app.use(function (client, msg, next) {
  // client is an MQTT client instance
  // msg is an object with 2 property: topic <String>, data <Buffer>
  // next is a function to call to invoke the next middleware
})
 
// Broker
app.use(function(broker, client, packet, next){
  // broker is a reference to our broker.
  // client is the sender mqtt client.
  // packet is the incoming packet, containes: .topic, .payload etc.
  // next is a function to call to invoke the next middleware
})

app.use(topic, fn)

Use a function on the app, where the function represents a middleware. The function will be invoked for every packet received in which the TOPIC match with the given topic string in the order that app.use is called.

app.use('/foo', function (client, msg, next) {
  // client is an MQTT client instance
  // msg is an object with 2 property: topic <String>, data <Buffer>
  // next is a function to call to invoke the next middleware
})
 
app.use('/bar/+', brokerCb)

The topic could be terminated with a path separator (/) or an MQTT wildcard character (+ or #). This means the given topic /foo/ and /foo are NOT the same and both will not match the same messages.

Moreover the topic is matched in a case-sensitive manor!

Check the mqtt-match module or the MQTT protocol documentation to better understand topic matching.

app.stack

Expose the function that will iterate through the added middlewares instances.

• For the Client could be called with 2 params (topic,msg).
• For the Broker could be called with 2 params (packet,client).

Common usage:

// Client
client.on('message', app.stack) // fn(topic, msg)
 
// Broker
server.on('published', app.stack) // fn(packet, client)

It's built to be compatible with the MQTT.js Module and the Mosca Broker. But it could also be used together with an EventEmitter class that emits messages following the same function signature.

app.getCount()

Returns the number of middlewares currently inside our MQTTConnect Client or Broker instance.

app.reset()

Removes all the middlewares from our app.

Author

Rocco Musolino (@roccomuso)

License

MIT