replyr

Replyer

Node.js MQTT client with built-in request and response methods

Replyer is a wrapper of MQTT.js client that expands its API with common use cases. It is completely compatible and interoperable, so in most projects you can upgrade by dropping:

var mqtt = require('replyer')

instead of var mqtt = require('mqtt').

Hello world

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

client.on('connect', function () {
  client.subscribe('chat')
  client.publish('chat', 'Hello replyer!')
})

client.on('chat', function (data) {
  console.log(data) // 'Hello replyer!'
  client.end()
})

Request and replyer

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

client.on('connect', function () {
  console.log('connected')
})

client.emit('network', { device: 'sensor' }, function (response) {
  console.log(response)
})

client.on('network', function (data, message) {
  console.log(data.device) // 'sensor'
  message.reply('got it')
  client.end()
})

Replyer scheme

This package is real time communication similar trying to join the best of both socket.io and MQTT.

It implements request and response with the same API as in socket.io to ease refactor. All clients are listening on their own id path as:

@client-id/message-id + /usual/mqtt/path

The ‘at’ symbol identifies a message as a MQTT request: it has to be addressed only to that particular client. #msg-id is an optional parameter to ensure that a certain reply is for a very particular request. In usual conditions we can count on this. Messages may get lost, for which timeouts are implemented. In case of a series of packets lost before a timeout, a client may interpret a wrong order, thus failing. So this little overhead for request/reply is really useful.