# clj-browserchannel

Cross-browser compatible, real-time, bi-directional
communication between ClojureScript and Clojure using Google Closure
BrowserChannel.

From the [Google Closure API][1]:

> A BrowserChannel simulates a bidirectional socket over HTTP. 
> It is the basis of the Gmail Chat IM connections to the server.

The JavaScript API of BrowserChannel is open-source and part of the
Google Closure library. The server component is not, as is noted in
the Google Closure book ("Closure: The Definitive Guide by Michael Bolin").

[1]: https://google.github.io/closure-library/api/source/closure/goog/net/browserchannel.js.src.html

## Usage

This project is comprised of multiple libraries. You'll need to include
two of them in your projects.

[clj-browserchannel][2] is the main library containing both the server- and
client-side functionality you'll use in your web apps.

In order to use the server implementation of BrowserChannel you'll need to
use one of the async adapters. Currently the provided options are:

* [clj-browserchannel-jetty-adapter][3]
* [clj-browserchannel-immutant-adapter][4]

[2]: https://github.com/gered/clj-browserchannel/tree/master/clj-browserchannel
[3]: https://github.com/gered/clj-browserchannel/tree/master/clj-browserchannel-jetty-adapter
[4]: https://github.com/gered/clj-browserchannel/tree/master/clj-browserchannel-immutant-adapter

You can find more information on usage of all of these components by
following any of the above links to them.

## Demo

The [chat-demo][5] application is an example chat application using a
client-side and server-side implementation for BrowserChannel written in
Clojure/ClojureScript. The server component is for BrowserChannel version 8.
The client component serves as a wrapper over `goog.net.BrowserChannel`
which also currently implements version 8 of the protocol.

[5]: https://github.com/gered/clj-browserchannel/tree/master/chat-demo

The chat-demo web app runs in at least:

* Chrome
* Firefox
* Internet Explorer 5.5+ (!!)
* Android browser
* Others

## Related and alternative frameworks

* Websockets - Websockets solve the same problems as BrowserChannel,
  however BrowserChannel works on almost all existing clients.
  Websockets ultimately replaces BrowserChannel.
* socket.io - [socket.io][6] provides a similar api as BrowserChannel on
  top of many transport protocols, including websockets. BrowserChannel
  only has two transport protocols: XHR and forever frames (for IE) in
  streaming and non-streaming mode.

[6]: http://socket.io

## Other BrowserChannel implementations
Many thanks to these authors, their work is the only open-source
documentation on the BrowserChannel protocol.

* [libevent-browserchannel-server][libevent]
in C++ by Andy Hochhaus - Has the most extensive documentation on the BrowserChannel protocol (dead project?). See the protocol documentation on [archive.org][libevent-doc].
* [browserchannel][ruby] in Ruby by David Turnbull (dead project?)
* [node-browserchannel][node]
in Node.js/Javascript by Joseph Gentle

[libevent]: http://code.google.com/p/libevent-browserchannel-server
[libevent-doc]: http://web.archive.org/web/20121226064550/http://code.google.com/p/libevent-browserchannel-server/wiki/BrowserChannelProtocol
[ruby]: https://github.com/dturnbull/browserchannel
[node]: https://github.com/josephg/node-browserchannel

## About

Written by:
Gijs Stuurman /
[@thegeez](http://twitter.com/thegeez) /
[Blog](http://thegeez.github.com) /
[GitHub](https://github.com/thegeez)

Many updates in this fork by:
Gered King /
[@geredking](http://twitter.com/geredking) /
[GitHub](https://github.com/gered)

### License

Copyright (c) 2012 Gijs Stuurman and released under an MIT license.