How to update a window content from server side

I searched the forum and didn’t find a posting on this. Can someone point me to a method to update window content after it is posted on client side? The usecase is, I display a panel, then without any user action (push button etc.), I want to update the content of this panel or close it from server side, all based on decision made on server side. Is this possible?

Server Push
Updating UI from another thread

Agata: Thank you for the respond. I forgot to mention I am limited to use vaadin 6 right now. Does server push add-on work in v6? The “Updating UI from another thread” link also mentioned about a client pulling method via some refresher component. Is the refresher component available in vaadin 6? Thanks.