socket.io

Sockets for the rest of us

The socket.io client is basically a simple HTTP Socket interface implementation. It allows you to establish a realtime connection with a server (see socket.io server here), hiding the complexity of the different transports (WebSocket, Flash, forever iframe, XHR long polling, XHR multipart encoded, etc), while retaining a WebSocket-like API:

socket = new io.Socket('localhost');
socket.connect();
socket.on('connect', function(){
	// connected
});
socket.on('message', function(data){
	// data here
});
socket.send('some data');

Features

• Supports

  • WebSocket
  • Adobe Flash Socket
  • ActiveX HTMLFile (IE)
  • XHR with multipart encoding
  • XHR with long-polling
  • JSONP polling (for cross-domain)

• Tested on

  • Safari 4
  • Google Chrome 5
  • Internet Explorer 6
  • Internet Explorer 7
  • Internet Explorer 8
  • iPhone Safari
  • iPad Safari
  • Firefox 3
  • Firefox 4 (Minefield)
  • Opera 10.61

• ActionScript Socket is known not to work behind proxies, as it doesn't have access to the user agent proxy settings to implement the CONNECT HTTP method. If it fails, socket.io will try something else.

• On a successful connection, it remembers the transport for next time (stores it in a cookie).

• Small. Closure Compiled with all deps: 5.82kb (gzipped).

• Easy to use! See socket.io-node for the server to connect to.

How to use

socket = new io.Socket('localhost');
socket.connect();
socket.send('some data');
socket.on('message', function(data){
	alert('got some data' + data);
});

For an example, check out the chat source.

Notes

If you are serving you .swf from a other domain than socket.io.js you will need to change the WEB_SOCKET_SWF_LOCATION to the insecure version.

<script>WEB_SOCKET_SWF_LOCATION = '/path/to/WebSocketMainInsecure.swf';</script>

The insecure version can be found here.

Documentation

io.Socket

new io.Socket(host, [options]);

Options:

• secure

    false
  

  Use secure connections

• port

    Current port or 80
  

  The port socket.io server is attached to (defaults to the document.location port).

• resource

    socket.io
  

  The resource is what allows the socket.io server to identify incoming connections by socket.io clients. In other words, any HTTP server can implement socket.io and still serve other normal, non-realtime HTTP requests.

• transports

    ['websocket', 'flashsocket', 'htmlfile', 'xhr-multipart', 'xhr-polling', 'jsonp-polling']
  

  A list of the transports to attempt to utilize (in order of preference).

• transportOptions

    {
    	someTransport: {
    		someOption: true
    	},
    	...
    }
  

  An object containing (optional) options to pass to each transport.

• rememberTransport

    true
  

  A boolean indicating if the utilized transport should be remembered in a cookie.

• connectTimeout

    5000
  

  The amount of miliseconds a transport has to create a connection before we consider it timed out.

• tryTransportsOnConnectTimeout

    true
  

  A boolean indicating if we should try other transports when the connectTimeout occurs.

• reconnect

    true
  

  A boolean indicating if we should automatically reconnect if a connection is disconnected.

• reconnectionDelay

    500
  

  The amount of milliseconds before we try to connect to the server again. We are using a exponential back off algorithm for the following reconnections, on each reconnect attempt this value will get multiplied (500 > 1000 > 2000 > 4000 > 8000).

• maxReconnectionAttempts

    10
  

  The amount of attempts should we make using the current transport to connect to the server? After this we will do one final attempt, and re-try with all enabled transport methods before we give up.

Properties:

• options

  The passed in options combined with the defaults.

• connected

  Whether the socket is connected or not.

• connecting

  Whether the socket is connecting or not.

• reconnecting

  Whether we are reconnecting or not.

• transport

  The transport instance.

Methods:

• connect

  Establishes a connection.

• send(message)

  A string of data to send.

• disconnect

  Closes the connection.

• on(event, λ)

  Adds a listener for the event event.

• removeEvent(event, λ)

  Removes the listener λ for the event event.

Events:

• connect

  Fired when the connection is established and the handshake successful.

• connecting(transport_type)

  Fired when a connection is attempted, passing the transport name.

• connect_failed

  Fired when the connection timeout occurs after the last connection attempt. This only fires if the connectTimeout option is set. If the tryTransportsOnConnectTimeout option is set, this only fires once all possible transports have been tried.

• message(message)

  Fired when a message arrives from the server

• close

  Fired when the connection is closed. Be careful with using this event, as some transports will fire it even under temporary, expected disconnections (such as XHR-Polling).

• disconnect

  Fired when the connection is considered disconnected.

• reconnect(transport_type,reconnectionAttempts)

  Fired when the connection has been re-established. This only fires if the reconnect option is set.

• reconnecting(reconnectionDelay,reconnectionAttempts)

  Fired when a reconnection is attempted, passing the next delay for the next reconnection.

• reconnect_failed

  Fired when all reconnection attempts have failed and we where unsucessfull in reconnecting to the server.

Contributors

Guillermo Rauch <guillermo@learnboost.com>

Arnout Kazemier <info@3rd-eden.com>

License

(The MIT License)

Copyright (c) 2010 LearnBoost <dev@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.