Sorry for the long delay in answering. When attempting to load a marshaller, org.jboss.remoting.marshal.MarshalFactory will first try to use the value of the datatype parameter, "invocation" in this case. Since "invocation" is not a built-in data type, there would be no marshaller associated with "invocation" unless you explicitly made the connection by calling MarshalFactory.addMarshaller(). Did you do that? If not, that's ok, since it will then look in the InvokerLocator for the fully qualified name of a marshaller. So, in your case, it should create an instance of com.test.socket.V75SocketServer.TextMarshaller. I don't know why it isn't. Could you run your application with TRACE logging turned on to see if there are any messages concerning the marshaller? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4072863#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...