thirst and thrust

Comet is a programming technique that enables web servers to send data to the client without having any need for the client to request it.

In classic AJAX applications, web browser (client) cannot be notified in real time that the server data model has changed. The user must create a request (for example by clicking on a link) or a periodic AJAX request must happen in order to get new data from the server.

As I am discovering this is not a straight forward technique. Comet can be very resource intensive. It is interesting to note that most commercial or referenced implementation of comet involves custom written web-servers designed to handle the requirements of this technique to specifically deal with the many detractors. Having to deal with lost connection, proxies that cache portions of response, and firewalls that automatically close HTTP streams after a certain period (to name a few) are all issues that may need to be addressed when attempting to implement comet.

In a current personal project I need to implement a push from the server so that it can notify users of events caused a particular user causes an event to happen on the server. In essence there will be a shared application state that users can affect and there is a need for all users in the same ’server session’ to be notified. I am going to explore my options and comet was the first thing I ran across showing promise.

Stay tuned.

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