engine.io-client

Client for the realtime Engine

npm install engine.io-client
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Engine.IO client

Build Status NPM version

This is the client for Engine.IO, the implementation of transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO.

How to use

Standalone

You can find an engine.io.js file in this repository, which is a standalone build you can use as follows:

<script src="/path/to/engine.io.js"></script>
<script>
  // eio = Socket
  var socket = eio('ws://localhost');
  socket.onopen = function(){
    socket.onmessage = function(data){};
    socket.onclose = function(){};
  };
</script>

With browserify

Engine.IO is a commonjs module, which means you can include it by using require on the browser and package using browserify:

  1. install the client package

    npm install engine.io-client
    
  2. write your app code

    var socket = require('engine.io-client')('ws://localhost');
    socket.onopen = function(){
     socket.onmessage = function(data){};
     socket.onclose = function(){};
    };
    
  3. build your app bundle

    $ browserify app.js > bundle.js
    
  4. include on your page

    <script src="/path/to/bundle.js"></script>
    

Sending and receiving binary

<script src="/path/to/engine.io.js"></script>
<script>
  var socket = new eio.Socket('ws://localhost/');
  socket.binaryType = 'blob'; // receives Blob instead of ArrayBuffer (default)
  socket.on('open', function () {
    socket.send(new Int8Array(5));
    socket.on('message', function (data) {
      // data instanceof Blob => true when receiving binary
    });
    socket.on('close', function () { });
  });
</script>

Node.JS

Add engine.io-client to your package.json and then:

var socket = require('engine.io-client')('ws://localhost');
socket.onopen = function(){
  socket.onmessage = function(data){};
  socket.onclose = function(){};
};

Features

  • Lightweight
    • Lazyloads Flash transport
  • Isomorphic with WebSocket API
  • Runs on browser and node.js seamlessly
  • Transports are independent of Engine
    • Easy to debug
    • Easy to unit test
  • Runs inside HTML5 WebWorker
  • Can send and receive binary data
    • Receives as ArrayBuffer or Blob when in browser, and Buffer or ArrayBuffer in Node
    • When XHR2 or WebSockets are used, binary is emitted directly. Otherwise binary is encoded into base64 strings, and decoded when binary types are supported.
    • With browsers that don't support ArrayBuffer, an object { base64: true, data: dataAsBase64String } is emitted in onmessage

API

Socket

The client class. Mixes in Emitter. Exposed as eio in the browser standalone build.

Properties

  • protocol (Number): protocol revision number
  • onopen (Function)
    • open event handler
  • onmessage (Function)
    • message event handler
  • onclose (Function)
    • message event handler
  • binaryType (String) : can be set to 'arraybuffer' or 'blob' in browsers, and buffer or arraybuffer in Node. Blob is only used in browser if it's supported.

Events

  • open
    • Fired upon successful connection.
  • message
    • Fired when data is received from the server.
    • Arguments
      • String | ArrayBuffer: utf-8 encoded data or ArrayBuffer containing binary data
  • close
    • Fired upon disconnection. In compliance with the WebSocket API spec, this event may be fired even if the open event does not occur (i.e. due to connection error or close()).
  • error
    • Fired when an error occurs.
  • flush
    • Fired upon completing a buffer flush
  • drain
    • Fired after drain event of transport if writeBuffer is empty
  • upgradeError
    • Fired if an error occurs with a transport we're trying to upgrade to.
  • upgrade
    • Fired upon upgrade success, after the new transport is set

Methods

  • constructor
    • Initializes the client
    • Parameters
      • String uri
      • Object: optional, options object
    • Options
      • agent (http.Agent): http.Agent to use, defaults to false (NodeJS only)
      • upgrade (Boolean): defaults to true, whether the client should try to upgrade the transport from long-polling to something better.
      • forceJSONP (Boolean): forces JSONP for polling transport.
      • forceBase64 (Boolean): forces base 64 encoding for polling transport even when XHR2 responseType is available and WebSocket even if the used standard supports binary.
      • timestampRequests (Boolean): whether to add the timestamp with each transport request. Note: this is ignored if the browser is IE or Android, in which case requests are always stamped (false)
      • timestampParam (String): timestamp parameter (t)
      • flashPath (String): path to flash client files with trailing slash
      • policyPort (Number): port the policy server listens on (843)
      • path (String): path to connect to, default is /engine.io
      • transports (Array): a list of transports to try (in order). Defaults to ['polling', 'websocket', 'flashsocket']. Engine always attempts to connect directly with the first one, provided the feature detection test for it passes.
      • rememberUpgrade (Boolean): defaults to false. If true and if the previous websocket connection to the server succeeded, the connection attempt will bypass the normal upgrade process and will initially try websocket. A connection attempt following a transport error will use the normal upgrade process. It is recommended you turn this on only when using SSL/TLS connections, or if you know that your network does not block websockets.
  • send
    • Sends a message to the server
    • Parameters
      • String | ArrayBuffer | ArrayBufferView | Blob: data to send
      • Function: optional, callback upon drain
  • close
    • Disconnects the client.

Transport

The transport class. Private. Inherits from EventEmitter.

Events

  • poll: emitted by polling transports upon starting a new request
  • pollComplete: emitted by polling transports upon completing a request
  • drain: emitted by polling transports upon a buffer drain

Flash transport

In order for the Flash transport to work correctly, ensure the flashPath property points to the location where the files web_socket.js, swfobject.js and WebSocketMainInsecure.swf are located.

These files can be found here https://github.com/gimite/web-socket-js.git

Tests

engine.io-client is used to test engine. Running the engine.io test suite ensures the client works and vice-versa.

Browser tests are run using zuul. You can run the tests locally using the following command.

./node_modules/.bin/zuul --local 8080 -- test/index.js

Additionally, engine.io-client has a standalone test suite you can run with make test which will run node.js and browser tests. You must have zuul setup with a saucelabs account.

Support

The support channels for engine.io-client are the same as socket.io:

Development

To contribute patches, run tests or benchmarks, make sure to clone the repository:

git clone git://github.com/LearnBoost/engine.io-client.git

Then:

cd engine.io-client
npm install

See the Tests section above for how to run tests before submitting any patches.

License

(The MIT License)

Copyright (c) 2014 Guillermo Rauch <guillermo@learnboost.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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