Hi. I have been checking your Instant Messenger Application. As I noted, you are using GWT-RPC. What if you want to use HTTP live connections (like GMail built in messenger)? How to do this in GWT? Thanks.
I not sure what you mean by HTTP live connections.
One restriction with HTTP is that every response needs a matching request. The server can't just send data to the client when necessary. This is sometimes called server push or HTTP events. I'll assume this is what you're referring to.
The instant messenger application in chapter 9 tackles the issue of server push with Ajax applications. It looks at polling(bad), hanging HTTP calls(better), and then looks at solutions with advanced IO on Tomcat and Continuations on Jetty where hanging waits don't hang threads as well, thereby improving performance dramatically(best).
I hope this answers your question. By using these techniques you can get server push like you see in GMail.