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This repository contains JavaScript client for both NodeJS and the Browser for Emitter (see also on Emitter GitHub). Emitter is an open-source real-time communication service for connecting online devices. At its core, emitter.io is a distributed, scalable and fault-tolerant publish-subscribe messaging platform based on MQTT protocol and featuring message storage.

Installation

Emitter for NodeJS:

npm install emitter-io --save

Emitter for the Browser:

Example

// connect to emitter.io and get the client
var client = emitter.connect(); // or: require('emitter-io') on NodeJS 

// once we're connected, subscribe to the 'chat' channel
client.subscribe({
	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
client.publish({
	key: "<channel key>",
	channel: "chat/my_name",
	message: "hello, emitter!"
});

API

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.

Emitter()

The Emitter class wraps a client connection to an emitter.io 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 'keygen'

function(keyJson) {}

Emitted when the client generate a key to a channel using Emitter#keygen() function.

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#disconnect()

Disconnects from the remote broker

Emitter#link({ key: string; channel: string; name: string; private: boolean; message: any; ttl?: number; me?: boolean; })

Creates a 2-character link to a channel. The channel may be private. For more information about this feature, see Emitter: Simplify Client/Server and IoT Apps with Links and Private Links (on YouTube) and the Emitter Pull Request (on GitHub).

  • key is security key to use for the operation, String
  • channel is the channel string to publish to, String
  • name is the 2-character name of the link, String
  • private requests the creation of a private channel, Boolean
  • message is the message to publish, Buffer or String
  • ttl is the time to live of the messages that will be sent through the link, Number.
  • me tells whether the messages sent through the link should be also sent to the publisher, Boolean. By default it is set to true.

See also publishWithLink().

Emitter#publish({ key: string; channel: string; message: any; ttl?: number; me?: boolean; })

Publishes 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
  • ttl is the time to live of the message, Number
  • me tells whether the messages should be also sent to the publisher, Boolean. By default it is set to true.

Emitter#publishWithLink({ link: string; message: any; })

Publishes a message to a link.

  • link is the name of the link, String
  • message is the message to publish, Buffer or String

See also link().

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, p for presence only and rw for read-write keys (In addition to rw, you can use any combination of r, w and p for key generation), String
  • ttl is the time-to-live of the key, in seconds.

Emitter#me()

Retrieves information about the underlying client connection. Information includes the client ID and the links created by the client.

Emitter#presence({ key: string; channel: string; status: boolean; changes: boolean; })

Requests the presence for a particular channel.

  • key is master/secret key to use for the operation, String
  • channel is the channel string to generate a key for, String
  • status whether the current state should be retrieved or not
  • changes whether the future changes should be received or not

EmitterMessage()

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

EmitterMessage#asString()

Returns the payload as a utf-8 String.

EmitterMessage#asBinary()

Returns the payload as the Buffer.

EmitterMessage#asObject()

Returns the payload as JSON-deserialized Object.

License

The MIT License (MIT) Copyright (c) 2016 Misakai Ltd.