node.websocket.js

node.websocket.js is an experimental implementation of the Web Socket protocol for the Evented I/O API Node.js.

The end goal of the project is to provide an abstraction layer of the protocol used to support different communication schemes through a simple-to-use API. As such, node.websocket.js should be able to work with UAs that use alternative connection methods (xhr streaming, long-polling, forever iframe).

Requirements

• Node.js (tested with v0.1.21)

Optional:

• Redis used for logging. redis-node-client is included. See log.js for the benefits of Redis as a logging mechanism.

How to use

Run the server:

$ node runserver.js

By default, it'll listen on localhost port 8080. node.websocket.js interprets the arguments passed in and turns those into the object passed to the websocket::Server constructor:

$ node runserver.js --port='8080' --host='some_other_host' --origins=['http://some_allowed_host']

The option values are eval()'d to turn them into native JavaScript types, so don't forget to wrap strings in ' '.

On the client side, initialize a WebSocket like this:

new WebSocket(ws://localhost:8080/test);

websocket::Connection will try to load a module in the modules/ directory with the name of the passed resource (in this case test).

If the resource is just / (for example ws://localhost:8080/), modules/_default.js will be loaded. The module has to expose a Module pseudoclass with an onData method like this:

var Module = this.Module = function(){
	// constructor;
};

Module.prototype.onData = function(data, instance){
	// do something 
};

The second parameter received is the websocket::Connection instance. To send data back to the client your module should do something like this:

Module.prototype.onData = function(data, connection){
	connection.send('sending data!');
}

Additionally, you can implement an onDisconnect method, called when a Connection finishes.

Features

• Very clean API that you can extend.

• It's easy to handle different resources as modules through Node dependency injection.

• Support for flash policy requests (for flash-based WebSocket emulation for old browsers). Thanks @joewalnes!

Demonstration

Here's a screenshot of the demo that comes with node.websocket.js:

In order to run it by yourself, download and compile redis and run it in a terminal

$ ./redis-server

While redis is simply used for logs storage here (and its not indispensable), I highly encourage you to discover and examine its potential.

In a different terminal, as described above, run node.webserver.js:

$ node runserver.js

Access test/test.html (which you can run locally or deliver through any web server, such as Apache) and watch true realtime data exchange!

Other Examples

The modules folder contains a few more demos:

• echo.js - a basic echo server
• processes.js - shows the output of a "ps" command every 5 seconds
• chat.js - a port of the nodechat to node.websockets

The try them out, you can use the html fies in test/websockets. Please also note that these integrate web-socket-js to support non-Chrome browsers.

TODO

• Support for WebSocket-Protocol header, and additional HTTP headers such as Cookie. WebSocket-Protocol support is optional, so node.websocket is still spec-compliant.
• Support for wss:// and TLS handshake
• More strict URI parsing/validation

Author

Guillermo Rauch <http://devthought.com>