One of the goals of Play2 architecture is to provide a programming model for what is called Realtime Web Applications.
Realtime Web Applications are applications making use of Websockets, Server Sent Events, Comet or other protocols offering/simulating an open socket between the browser and the server for continuous communication. Basically, these applications offer to users delivery of information as it is published without having the user periodically pinging the service.
There are quite a few web frameworks that target the development of this type of applications. Mostly, however, the solution is by providing an API that allows developers to push/receive messages from/to an open channel, something like: