Hello: I want to ask if i need do the port stuff for rmi, i mean use different port to run servers, but then we cannot do the lock map correctly. must i make the lock and unlock methods synchronized? Is a synchronized map helpful? because some of the people here said it was correct, but some said it was not correct. when i use a local acess mode, it is ok that my GUI directly calls the data class? now in my design, i only call the dataClient which will connect with the DataServer in remote mode.