JarCastingmqtt-packet
Encode and Decode MQTT 3.1.1, 5.0 packets the node way.
This library is tested with node v6, v8, v10, v12 and v14. The last version to support older versions of node was [email protected].
Installation
npm install mqtt-packet --save
Examples
Generating
const mqtt = require('mqtt-packet');
const object = {
cmd: 'publish',
retain: false,
qos: 0,
dup: false,
length: 10,
topic: 'test',
payload: 'test' // Can also be a Buffer
};
const opts = { protocolVersion: 4 }; // default is 4. Usually, opts is a connect packet
console.log(mqtt.generate(object))
// Prints:
//
// <Buffer 30 0a 00 04 74 65 73 74 74 65 73 74>
//
// Which is the same as:
//
// Buffer.from([
// 48, 10, // Header (publish)
// 0, 4, // Topic length
// 116, 101, 115, 116, // Topic (test)
// 116, 101, 115, 116 // Payload (test)
// ])
Parsing
const mqtt = require('mqtt-packet');
const opts = { protocolVersion: 4 }; // default is 4. Usually, opts is a connect packet
const parser = mqtt.parser(opts);
// Synchronously emits all the parsed packets
parser.on('packet', 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(Buffer.from([
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(object, [opts])
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, [opts])
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([opts])
Returns a new Parser object. Parser inherits from EventEmitter and will emit:
packet, when a new packet is parsed, according to packetserror, 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 and 5.0
protocolVersion: 4, // Or 3 in MQTT 3.1, or 5 in MQTT 5.0
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: Buffer.from('collina'), // Passwords are buffers
will: {
topic: 'mydevice/status',
payload: Buffer.from('dead'), // Payloads are buffers
properties: { // MQTT 5.0
willDelayInterval: 1234,
payloadFormatIndicator: false,
messageExpiryInterval: 4321,
contentType: 'test',
responseTopic: 'topic',
correlationData: Buffer.from([1, 2, 3, 4]),
userProperties: {
'test': 'test'
}
}
},
properties: { // MQTT 5.0 properties
sessionExpiryInterval: 1234,
receiveMaximum: 432,
maximumPacketSize: 100,
topicAliasMaximum: 456,
requestResponseInformation: true,
requestProblemInformation: true,
userProperties: {
'test': 'test'
},
authenticationMethod: 'test',
authenticationData: Buffer.from([1, 2, 3, 4])
}
}
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 MQTT < 5.0
sessionPresent: false, // Can also be true.
reasonCode: 0, // reason code MQTT 5.0
properties: { // MQTT 5.0 properties
sessionExpiryInterval: 1234,
receiveMaximum: 432,
maximumQoS: 2,
retainAvailable: true,
maximumPacketSize: 100,
assignedClientIdentifier: 'test',
topicAliasMaximum: 456,
reasonString: 'test',
userProperties: {
'test': 'test'
},
wildcardSubscriptionAvailable: true,
subscriptionIdentifiersAvailable: true,
sharedSubscriptionAvailable: false,
serverKeepAlive: 1234,
responseInformation: 'test',
serverReference: 'test',
authenticationMethod: 'test',
authenticationData: Buffer.from([1, 2, 3, 4])
}
}
The only mandatory argument is returnCode, as generate will throw if missing.
Subscribe
{
cmd: 'subscribe',
messageId: 42,
properties: { // MQTT 5.0 properties
subscriptionIdentifier: 145,
userProperties: {
test: 'test'
}
}
subscriptions: [{
topic: 'test',
qos: 0,
nl: false, // no Local MQTT 5.0 flag
rap: true, // Retain as Published MQTT 5.0 flag
rh: 1 // Retain Handling MQTT 5.0
}]
}
All properties are mandatory.
Suback
{
cmd: 'suback',
messageId: 42,
properties: { // MQTT 5.0 properties
reasonString: 'test',
userProperties: {
'test': 'test'
}
}
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,
properties: { // MQTT 5.0 properties
userProperties: {
'test': 'test'
}
}
unsubscriptions: [
'test',
'a/topic'
]
}
All properties are mandatory.
Unsuback
{
cmd: 'unsuback',
messageId: 42,
properties: { // MQTT 5.0 properties
reasonString: 'test',
userProperties: {
'test': 'test'
}
}
}
All properties are mandatory.
Publish
{
cmd: 'publish',
messageId: 42,
qos: 2,
dup: false,
topic: 'test',
payload: Buffer.from('test'),
retain: false,
properties: { // optional properties MQTT 5.0
payloadFormatIndicator: true,
messageExpiryInterval: 4321,
topicAlias: 100,
responseTopic: 'topic',
correlationData: Buffer.from([1, 2, 3, 4]),
userProperties: {
'test': 'test'
},
subscriptionIdentifier: 120, // can be an Array in message from broker, if message included in few another subscriptions
contentType: 'test'
}
}
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,
reasonCode: 16, // only for MQTT 5.0
properties: { // MQTT 5.0 properties
reasonString: 'test',
userProperties: {
'test': 'test'
}
}
}
The only mandatory property is messageId, as generate will throw if missing.
Pubrec
{
cmd: 'pubrec',
messageId: 42,
reasonCode: 16, // only for MQTT 5.0
properties: { // properties MQTT 5.0
reasonString: 'test',
userProperties: {
'test': 'test'
}
}
}
The only mandatory property is messageId, as generate will throw if missing.
Pubrel
{
cmd: 'pubrel',
messageId: 42,
reasonCode: 16, // only for MQTT 5.0
properties: { // properties MQTT 5.0
reasonString: 'test',
userProperties: {
'test': 'test'
}
}
}
The only mandatory property is messageId, as generate will throw if missing.
Pubcomp
{
cmd: 'pubcomp',
messageId: 42,
reasonCode: 16, // only for MQTT 5.0
properties: { // properties MQTT 5.0
reasonString: 'test',
userProperties: {
'test': 'test'
}
}
}
The only mandatory property is messageId, as generate will throw if missing.
Pingreq
{
cmd: 'pingreq'
}
Pingresp
{
cmd: 'pingresp'
}
Disconnect
{
cmd: 'disconnect',
reasonCode: 0, // MQTT 5.0 code
properties: { // properties MQTT 5.0
sessionExpiryInterval: 145,
reasonString: 'test',
userProperties: {
'test': 'test'
},
serverReference: 'test'
}
}
Auth
{
cmd: 'auth',
reasonCode: 0, // MQTT 5.0 code
properties: { // properties MQTT 5.0
authenticationMethod: 'test',
authenticationData: Buffer.from([0, 1, 2, 3]),
reasonString: 'test',
userProperties: {
'test': 'test'
}
}
}
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 |
| Siarhei Buntsevich | GitHub/scarry1992 |
License
MIT
