XMPP: powering the real-time, really live web

June 12, 2009 | 7 comments

When Google Wave was previewed last week, most people focused on its Gmail-like user interface and the slick way it handled collaborative spaces in real time. What was more exciting from a web technology point of view, although much less sexy, was the underlying protocol: Google Wave is built on top of an extended version of an open source real-time data standard called XMPP (aka Jabber when it’s used as an instant messaging context). This means that anyone can build servers and end-user applications that are compatible with Wave.

Yesterday, the BBC announced that they were using an open source framework called Hemlock in order to provide real-time web games on their Childrens’ site. Hemlock’s interfaces are built in Flash, but the real-time aspect is powered by XMPP. Developer Ron DeVera explained why over on the Hemlock blog:

XMPP is commonly used to enable chatrooms, like Gtalk or Facebook Chat. However, instead of just sending text, Hemlock lets you send all kinds of data at the speed of instant messaging. Even better, XMPP is designed to scale up and send data to many people at once, so you can push that data to multiple people in real-time.

In other words, it’s perfect for real-time applications on the web.

Traditionally, live web applications have used a development methodology called AJAX, which stands for Asynchronous Javascript And XML. In order to provide the illusion of a real-time application, the web browser needs to continue to ask the server if there’s any new data to ask, via a new AJAX request – which is a waste of bandwidth and resources both on the user and server side. XMPP, on the other hand, pings the client software whenever there’s new data.

Servers already need software to host and process dynamic web pages, as well as a database server to handle most types of user data. To use XMPP, you need to add an XMPP server to the mix – something that in the past was more fiddly than most people were willing to play with. However, times have changed, and ejabberd is free, open source and easy to install on Windows, Mac OS X and Linux servers. (I’m still at the early stages of playing with it; I’ll let you know how I get on.)

The XMPP community is still very small compared to the wider web, but developments like Wave and Hemlock should accelerate growth and interest in it. There are some interesting projects springing up, and lots of libraries available for XMPP development; XMPP programming is a skill developers should get in on now, before it really heats up.