engine.io-client

What is engine.io-client?

The engine.io-client npm package is a client-side library that provides bidirectional event-based communication between web clients and servers. It is the client component of the Engine.IO protocol, which is a transport layer built on top of WebSocket and other transport mechanisms to provide a reliable, low-latency connection for real-time applications.

What are engine.io-client's main functionalities?

Establishing a connection

This feature allows you to establish a connection to an Engine.IO server. The 'open' event is emitted when the connection is successfully established.

const eio = require('engine.io-client');
const socket = eio('ws://localhost');
socket.on('open', function(){
  console.log('Connection established');
});

Sending messages

Once a connection is established, you can send messages to the server using the 'send' method.

socket.send('Hello World!');

Receiving messages

You can listen for messages from the server with the 'message' event. The callback function receives the message data as its argument.

socket.on('message', function(data){
  console.log('Received message:', data);
});

Handling connection errors

The 'error' event is emitted when there is a connection error. The callback function receives the error object as its argument.

socket.on('error', function(error){
  console.error('Connection error:', error);
});

Closing the connection

The 'close' event is emitted when the connection is closed. The callback function receives the reason and a description as arguments.

socket.on('close', function(reason, description){
  console.log('Connection closed', reason, description);
});

Other packages similar to engine.io-client

socket.io-client

Socket.IO-client is a more feature-rich client-side library that provides real-time bidirectional event-based communication, similar to engine.io-client. It is built on top of engine.io-client and adds additional features like namespaces, rooms, and automatic reconnection.

ws

The 'ws' package is a simple WebSocket client and server implementation for Node.js. Unlike engine.io-client, it does not provide built-in mechanisms for features like automatic reconnection and binary data handling, but it allows for more control over the WebSocket connection.

faye-websocket

Faye-websocket is a WebSocket client and server for Node.js and Ruby. It provides a simple API for handling WebSocket connections but does not include the higher-level abstractions and fallback mechanisms that engine.io-client offers.

README

Engine.IO client

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

Hello World

With component

Engine.IO is a component, which means you can include it by using require on the browser:

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

Standalone

If you decide not to use component you can find a engine.io.js file in this repository, which is a standalone build you can use as follows:

<script src="/path/to/build.js"></script>
<script>
  // eio = Socket
  var socket = eio('ws://localhost');
  socket.onopen = function(){
    socket.onmessage = function(data){};
    socket.onclose = 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
• Written for node, runs on browser thanks to browserbuild
  • Maximizes code readability / maintenance.
  • Simplifies testing.
• Transports are independent of Engine
  • Easy to debug
  • Easy to unit test
• Runs inside HTML5 WebWorker

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

Events

• open
  • Fired upon successful connection.
• message
  • Fired when data is received from the server.
  • Arguments
    • String: utf-8 encoded data
• close
  • Fired upon disconnection.
• error
  • Fired when an error occurs.
• flush
  • Fired upon completing a buffer flush
• drain
  • Fired after drain event of transport if writeBuffer is empty

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.
    • 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)
    • 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.
• send
  • Sends a message to the server
  • Parameters
    • String: 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

Reconnecting

A Socket instance can be reused. After closing (either by calling Socket#close() or network close), you can summon open again.

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.

Additionally, engine.io-client has a standalone test suite you can run with make test or in the browser with make test-browser.

Support

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

• irc.freenode.net #socket.io
• Google Groups
• Website

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

License

(The MIT License)

Copyright (c) 2011 Guillermo Rauch <[e-mail]>

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.