alexxnica / mqtt-packet

Parse and generate MQTT packets like a breeze in JS

mqtt-packet   

Encode and Decode MQTT 3.1.1 packets the node way.

• Installation
• Examples
• Packets
• API
• Contributing
• License & copyright

This library is tested with node v4, v6 and v7. The last version to support older versions of node was [email protected].

Installation

npm install mqtt-packet --save

Examples

Generating

var mqtt = require('mqtt-packet')
var object = {
  cmd: 'publish',
  retain: false,
  qos: 0,
  dup: false,
  length: 10,
  topic: 'test',
  payload: 'test' // Can also be a Buffer
}

console.log(mqtt.generate(object))
// Prints:
//
// <Buffer 30 0a 00 04 74 65 73 74 74 65 73 74>
//
// Which is the same as:
//
// new Buffer([
//   48, 10, // Header (publish)
//   0, 4, // Topic length
//   116, 101, 115, 116, // Topic (test)
//   116, 101, 115, 116 // Payload (test)
// ])

Parsing

var mqtt = require('mqtt-packet')
var parser = mqtt.parser()

// Synchronously emits all the parsed packets
parser.on('packet', function(packet) {
  console.log(packet)
  // Prints:
  //
  // {
  //   cmd: 'publish',
  //   retain: false,
  //   qos: 0,
  //   dup: false,
  //   length: 10,
  //   topic: 'test',
  //   payload: <Buffer 74 65 73 74>
  // }
})

parser.parse(new Buffer([
  48, 10, // Header (publish)
  0, 4, // Topic length
  116, 101, 115, 116, // Topic (test)
  116, 101, 115, 116 // Payload (test)
])
// Returns the number of bytes left in the parser

API

• mqtt#generate()
• mqtt#writeToStream()
• mqtt#parser()

mqtt.generate(object)

Generates a Buffer containing an MQTT packet. The object must be one of the ones specified by the packets section. Throws an Error if a packet cannot be generated.

mqtt.writeToStream(object, stream)

Writes the mqtt packet defined by object to the given stream. The object must be one of the ones specified by the packets section. Emits an Error on the stream if a packet cannot be generated. On node >= 0.12, this function automatically calls cork() on your stream, and then it calls uncork() on the next tick. By default cache for number buffers is enabled. It creates a list of buffers for faster write. To disable cache set mqtt.writeToStream.cacheNumbers = false. Should be set before any writeToStream calls.

mqtt.parser()

Returns a new Parser object. Parser inherits from EventEmitter and will emit:

• packet, when a new packet is parsed, according to packets
• error, if an error happens

Parser.parse(buffer)

Parses a given Buffer and emits synchronously all the MQTT packets that are included. Returns the number of bytes left to parse.

If an error happens, an error event will be emitted, but no packet events will be emitted after that. Calling parse() again clears the error and previous buffer, as if you created a new Parser.

Packets

This section describes the format of all packets emitted by the Parser and that you can input to generate.

Connect

{
  cmd: 'connect',
  protocolId: 'MQTT', // Or 'MQIsdp' in MQTT 3.1.1
  protocolVersion: 4, // Or 3 in MQTT 3.1
  clean: true, // Can also be false
  clientId: 'my-device',
  keepalive: 0, // Seconds which can be any positive number, with 0 as the default setting
  username: 'matteo',
  password: new Buffer('collina'), // Passwords are buffers
  will: {
    topic: 'mydevice/status',
    payload: new Buffer('dead') // Payloads are buffers
  }
}

If protocolVersion is 3, clientId is mandatory and generate will throw if missing.

If password or will.payload are passed as strings, they will automatically be converted into a Buffer.

Connack

{
  cmd: 'connack',
  returnCode: 0, // Or whatever else you see fit
  sessionPresent: false // Can also be true.
}

The only mandatory argument is returnCode, as generate will throw if missing.

Subscribe

{
  cmd: 'subscribe',
  messageId: 42,
  subscriptions: [{
    topic: 'test',
    qos: 0
  }]
}

All properties are mandatory.

Suback

{
  cmd: 'suback',
  messageId: 42,
  granted: [0, 1, 2, 128]
}

All the granted qos must be < 256, as they are encoded as UInt8. All properties are mandatory.

Unsubscribe

{
  cmd: 'unsubscribe',
  messageId: 42,
  unsubscriptions: [
    'test',
    'a/topic'
  ]
}

All properties are mandatory.

Unsuback

{
  cmd: 'unsuback',
  messageId: 42
}

All properties are mandatory.

Publish

{
  cmd: 'publish',
  messageId: 42,
  qos: 2,
  dup: false,
  topic: 'test',
  payload: new Buffer('test'),
  retain: false
}

Only the topic property is mandatory. Both topic and payload can be Buffer objects instead of strings. messageId is mandatory for qos > 0.

Puback

{
  cmd: 'puback',
  messageId: 42
}

The only mandatory property is messageId, as generate will throw if missing.

Pubrec

{
  cmd: 'pubcomp',
  messageId: 42
}

The only mandatory property is messageId, as generate will throw if missing.

Pubrel

{
  cmd: 'pubrel',
  messageId: 42
}

The only mandatory property is messageId, as generate will throw if missing.

Pubcomp

{
  cmd: 'pubcomp',
  messageId: 42
}

The only mandatory property is messageId, as generate will throw if missing.

Pingreq

{
  cmd: 'pingreq'
}

Pingresp

{
  cmd: 'pingresp'
}

Disconnect

{
  cmd: 'disconnect'
}

Contributing

mqtt-packet 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-packet is only possible due to the excellent work of the following contributors:

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

License

MIT