Visual WebGui is based on ASP.NET that works over the Http protocol in the traditional Request/Response model, where the client must initiate the request in all cases.

Cometis a tecnology that allows the server to initiate a request to push changes to the client.

The need for the ability to have the server push changes to the client arises when you get some server side events fired and as a result of that you need to push something to the client, like updating the UI. When the server side has been updated, the client UI will only update on the next client's request to the server.

Using Visual WebGui controls only, it is possible to do this with the Timer, which will make sure the request will be sent to the server.

Comet technology is a way to make this work without using the Timer.

• Lightweight Comet control
  

• Google Wave and server push

• Weelya APE push engine and Wiki