How to do live updating similar to Google Docs?

Question

I want to do something very similar to Google Doc\'s live updating - where all users can \"immediately\" see the actions of the other users in the doc.

To achieve this,

Answer 1

I vote for Long-poll strategy : each client opens a request to the server, but the server never breaks up connections, and just send pieces of java-script from time to time.

Constant AJAX requests would kill your server.