C/S application - listener for a server remote call?

I'd like to know if there's any effective way how to deal with a situation when I need an Android client app to listen until it is called by a server - some kind of socket listener or so. I need the Android client app to be notified when server sends data, asynchronously. A simple example: I am running a chat service on server (Java app) and several Android clients connected and able to post messages. When any of the connected clients sends a message to the server, it processes it and notifies all other connected clients about this new post. Is there any effective way to do so? I do not much favor for the infinite loop workaround if there's better way. Thanks.

Hi,

In your question only the answer is hidden. Use services in android. They runs in background even if the application is in pause state. You can right your code which has implementation of socket programming.
I ma not sure android supports socket programming or not.(But I think it should support). Java has reach library for socket programming. Use it.