MQTT.js is a client library for the MQTT protocol, written in JavaScript for node.js and the browser.

• Upgrade notes
• Installation
• Example
• Command Line Tools
• API
• Contributing
• License

MQTT.js is an OPEN Open Source Project, see the Contributing section to find out what this means.

Important notes for existing users

v1.0.0 improves the overall architecture of the project, which is now splitted in three components: MQTT.js keeps the Client, mqtt-connection includes the barebone Connection code for server-side usage, and mqtt-packet includes the protocol parser and generator. The new Client improves performance by a 30% factor, embeds Websocket support (MOWS is now deprecated), and it has a better support for QoS 1 and 2. The previous API is still supported but deprecated, as such, it id not documented in this README.

As a breaking change, the encoding option in the old client is removed, and now everything is UTF-8 with the exception of the password in the CONNECT message and payload in the PUBLISH message.

Installation

npm install mqtt --save

Example

For the sake of simplicity, let's put the subscriber and the publisher in the same file:

var mqtt    = require('mqtt');
var client  = mqtt.connect('mqtt://test.mosquitto.org');

client.subscribe('presence');
client.publish('presence', 'Hello mqtt');

client.on('message', function (topic, message) {
  // message is Buffer
  console.log(message.toString());
});

client.end();

output:

Hello mqtt

If you want to run your own MQTT broker, you can use Mosquitto or Mosca, and launch it. You can also use a test instance: test.mosquitto.org and test.mosca.io are both public.

If you do not want to install a separate broker, you can try using the server/orig example. It implements enough of the semantics of the MQTT protocol to run the example.

Command Line Tools

MQTT.js bundles a command to interact with a broker. In order to have it available on your path, you should install MQTT.js globally:

npm install mqtt -g

Then, on one terminal

mqtt sub -t 'hello' -h 'test.mosquitto.org' -v

On another

mqtt pub -t 'hello' -h 'test.mosquitto.org' -m 'from MQTT.js'

See mqtt help <command> for the command help.

API

• mqtt.connect()
• mqtt.Client()
• mqtt.Client#publish()
• mqtt.Client#subscribe()
• mqtt.Client#unsubscribe()
• mqtt.Client#end()
• mqtt.Client#handleMessage()
• mqtt.Store()
• mqtt.Store#put()
• mqtt.Store#del()
• mqtt.Store#createStream()
• mqtt.Store#close()

---

mqtt.connect([url], options)

Connects to the broker specified by the given url and options and returns a Client.

The URL can be on the following protocols: 'mqtt', 'mqtts', 'tcp', 'tls', 'ws', 'wss'. The URL can also be an object as returned by URL.parse(), in that case the two objects are merged, i.e. you can pass a single object with both the URL and the connect options.

You can also specify a servers options with content: [{ host: 'localhost', port: 1883 }, ... ], in that case that array is iterated at every connect.

For all MQTT-related options, see the Client constructor.

---

mqtt.Client(streamBuilder, options)

The Client class wraps a client connection to an MQTT broker over an arbitrary transport method (TCP, TLS, WebSocket, ecc).

Client automatically handles the following:

• Regular server pings
• QoS flow
• Automatic reconnections
• Start publishing before being connected

The arguments are:

• streamBuilder is a function that returns a subclass of the Stream class that supports the connect event. Typically a net.Socket.
• options is the client connection options (see: the connect packet). Defaults:
  • keepalive: 10 seconds, set to 0 to disable
  • clientId: 'mqttjs'_ + crypto.randomBytes(16).toString('hex')
  • protocolId: 'MQTT'
  • protocolVersion: 4
  • clean: true, set to false to receive QoS 1 and 2 messages while offline
  • reconnectPeriod: 1000 milliseconds, interval between two reconnections
  • incomingStore: a Store for the incoming packets
  • outgoingStore: a Store for the outgoing packets

In case mqtts (mqtt over tls) is required, the options object is passed through to tls.connect().

Event 'connect'

function() {}

Emitted on successful (re)connection (i.e. connack rc=0).

Event 'close'

function() {}

Emitted after a disconnection.

Event 'offline'

function() {}

Emitted when the client goes offline.

Event 'error'

function(error) {}

Emitted when the client cannot connect (i.e. connack rc != 0) or when a parsing error occurs.

Event 'message'

function(topic, message, packet) {}

Emitted when the client recieves a publish packet

• topic topic of the received packet
• message payload of the received packet
• packet received packet, as defined in mqtt-packet

---

mqtt.Client#publish(topic, payload, [options])

Publish a message

• topic is the topic to publish to, String
• message is the message to publish, Buffer or String
• options is the options to publish with, including:
  • qos qos level, default 0
  • retain retain flag, default false
• callback callback fired when the QoS handling completes, or at the next tick if QoS 0.

---

mqtt.Client#subscribe(topic/topic array/topic object, [options], [callback])

Subscribe to a topic or topics

• topic is a String topic to subscribe to or an Array of topics to subscribe to. It can also be an object, it has as object keys the topic name and as value the QoS, like {'test1': 0, 'test2': 1}.
• options is the options to subscribe with, including:
  • qos qos subscription level, default 0
• callback - function(err, granted) callback fired on suback where:
  • err a subscription error
  • granted is an array of {topic, qos} where:
    • topic is a subscribed to topic
    • qos is the granted qos level on it

---

mqtt.Client#unsubscribe(topic/topic array, [options], [callback])

Unsubscribe from a topic or topics

• topic is a String topic or an array of topics to unsubscribe from
• callback fired on unsuback

---

mqtt.Client#end(cb)

Close the client, calls callback when finished.

---

mqtt.Client#handleMessage(packet, callback)

Handle messages with backpressure support, one at a time. Override at will, but always call callback, or the client will hang.

---

mqtt.Store()

In-memory implementation of the message store.

---

mqtt.Store#put(packet, callback)

Adds a packet to the store, a packet is anything that has a messageId property. The callback is called when the packet has been stored.

---

mqtt.Store#createStream()

Creates a stream with all the packets in the store.

---

mqtt.Store#del(packet, cb)

Removes a packet from the store, a packet is anything that has a messageId property. The callback is called when the packet has been removed.

---

mqtt.Store#close(cb)

Closes the Store.

Contributing

MQTT.js is an OPEN Open Source Project. This means that:

Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.

See the CONTRIBUTING.md file for more details.

Contributors

MQTT.js is only possible due to the excellent work of the following contributors:

Adam Rudd	GitHub/adamvr	Twitter/@adam_vr
Matteo Collina	GitHub/mcollina	Twitter/@matteocollina

License

MIT