public synchronized void setResponse( RpcResponseMessage msg ) {
            this.response = msg.getResult();
            this.error = msg.getError();
            this.exception = msg.getThrowable();
            this.received = true;
            notifyAll();
        }
Sort of like a Future, holds a locked reference to a response
 until the remote call has completed and returned a response.
jme3-networking/src/main/java/com/jme3/network/service/rpc/RpcConnection.java