BrainBlog is the Brains4All weblog. Established 2004 in The Netherlands. Brains have been working in IT since 1983, working on the internet since 1993, and using their own agile development process for design and application development since 2003. We talk about about design and usability, the industry of software and web development, web applications and simplicity, beautiful and spectacular things.




Alex Russell, from dojotoolkit, has found time in his busy schedule to dedicate an article to explaining about Server side push Ajax and has finally put a name on it: Comet. Alex hopes that analogous to AJAX, the technique will finally take off big-time when it is easier to communicate about by calling it by its name.

In short, Comet is the technique of continuously updating the browser screen by using server side pushed events instead of polling or pull events by the browser. In many ways the technique is similar or can be viewed as an extension to AJAX if you will. Alex describes possible scenarios for application as well. Not every web application is going to need it or even profit from it. "Comet improves application responsiveness for collaborative, multi-user applications..." A few obstacles are there to overcome, since each client browser has to maintain an open (if idle) connection to the server. Handling that amount of connections requires new techniques on the server side as well. Luckily for us, the discussion in the comments exposed an already flowering community and some server side techniques already implemented. Twisted seems to be a well cooked candidate, written in python. There's even an O'Reilly book out. What a formidable coincidence.

For more in-depth information check out: Alex Russells' blog entry. Ajaxpatterns on HTTPStreaming.

For those of you familiar with JotSpot live it is an example of a web 2.0 application using this technique.

An excellent introduction to twisted by Ken Kinder, Event-Driven Programming with Twisted and Python


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