Well, after some digging I found an way using JBoss CLI (just google a little about it and the special syntax called Detyped Management Model). With that in mind just call this command at the CLI:
/deployment=<YOUR-EAR-NAME>.ear/subdeployment=<YOUR-WAR-NAME>.war/subsystem=\"web\"/:read-attribute(name=active-sessions)
With that you can know the connected users for that specific war. This can be tunned with different ways to look for all wars, so just play with it. There's an API to do that programatically too.