This is the JavaScript library for the browser and NodeJS, built and maintained by team. The underlying communication layer uses MQTT.js and released under MIT license.



Emitter for NodeJS:

npm install emitter-io --save

Emitter for the Browser:


var client = emitter.connect(); 
// use require('emitter-io').connect() on NodeJS 

// once we're connected, subscribe to the 'chat' channel
	key: "<channel key>",
	channel: "chat"
// on every message, print it out
client.on('message', function(msg){
	console.log( msg.asString() );

// publish a message to the chat channel
	key: "<channel key>",
	channel: "chat/my_name",
	message: "hello, emitter!"


connect(host: string, port: number)

Connects to the emitter api broker specified by the given url and options and returns an Emitter instance. 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.


The Emitter class wraps a client connection to an MQTT broker over an arbitrary transport method (TCP, TLS, WebSocket, ecc). It automatically handles the following by with help of MQTT.js client:

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

Event 'connect'

function(connack) {}

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

  • connack received connack packet. When clean connection option is false and server has a previous session for clientId connection option, then connack.sessionPresent flag is true. When that is the case, you may rely on stored session and prefer not to send subscribe commands for the client.

Event 'disconnect'

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(message) {}

Emitted when the client receives a message packet. The message object will be of EmitterMessage class, encapsulating the channel and the payload.

Emitter#publish({ key: string; channel: string; message: any; })

Publish a message to a channel

  • key is security key to use for the operation, String
  • channel is the channel string to publish to, String
  • message is the message to publish, Buffer or String

Emitter#subscribe({ key: string; channel: string; })

Subscribes to a channel

  • key is security key to use for the operation, String
  • channel is the channel string to subscribe to, String

Emitter#unsubscribe({ key: string; channel: string; })

Unsubscribes from a channel

  • key is security key to use for the operation, String
  • channel is the channel string to unsubscribe from, String

Emitter#keygen({ key: string; channel: string; type: string; ttl: number; })

Sends a key generation request to the server.

  • key is master/secret key to use for the operation, String
  • channel is the channel string to generate a key for, String
  • type the type of the key to generate. Possible options include r for read-only, w for write-only and rw for read-write keys, String
  • ttl is the time-to-live of the key, in seconds.


Disconnects from the remote broker


The EmitterMessage class wraps a message received from the broker. It contains several properties:

  • channel is channel the message was published to, String
  • binary is the buffer associated with the payload, Buffer


Returns the payload as a utf-8 String.


Returns the payload as the Buffer.


Returns the payload as JSON-deserialized Object.