With former JBoss versions it was possible to pass context beside the method invocation from the client to the server and back. This was done via (AOP) interceptors.
Since AS7 and WildFly the only possibility is to pass such context from the client to the server.
It should also possible to pass serializeable objects from the server side to the client if the invocation returns and have a client side interceptor to read that informations.
This was used to return i.e. tracking or additional usefull informations.