public void registerHandler( short objId, RpcHandler handler ) {
        rpc.registerHandler(objId, handler);
    }
Register a handler that will be called when the server
 performs a remove procedure call against this client. 
 Only one handler per object ID can be registered at any given time,
 though the same handler can be registered for multiple object
 IDs.
jme3-networking/src/main/java/com/jme3/network/service/rpc/RpcClientService.java