Cannot disconnect client properly from server. RMI.

[Sven Sylta]

I have a Client-class that connects to my local-server without problem. I'm not sure how to disconnect it properly though. Thanks for your help(Maybe I need to explain more?).

class Client {

    private IServer s;

    @Override
    public void connect() {
        //Signals GUI
    	EventBus.INSTANCE.publish(new Event (Event.Tag.CONNECTED, Options.INSTANCE.getUser()));
    	
    	try {
    	        //This works fine.
        	Registry registry = LocateRegistry.getRegistry("127.0.0.1", 6666);
		 IServer s = (IServer) registry.lookup(Constants.MB_SERVER_NAME);
		
                //This adds a user in my Server-class	
	        s.register(Options.INSTANCE.getUser());
		
		} catch (RemoteException | NotBoundException e) {
			e.printStackTrace();
		}
    }
    
    @Override
    public void disconnect() {
         //Signals GUI
    	EventBus.INSTANCE.publish(new Event (Event.Tag.DISCONNECTED, Options.INSTANCE.getUser()));

             //This does not work
       try {
		UnicastRemoteObject.unexportObject(s, true);
      
		} catch (NoSuchObjectException e) {
			e.printStackTrace();
		}
    }
}

My Server-class

public class Server implements IServer {
   
    private final int registryPort;
    private final int serverPort;
  
    private List<User> users = new ArrayList<User>();

    public Server(int registryPort, int serverPort) {
        this.registryPort = registryPort;
        this.serverPort = serverPort;
    }
    
    @Override
    public String ping() throws RemoteException {
        return "Alive at serverPort " + serverPort + ". Registry port is " + registryPort;
    }

    //Make thread-safe
    @Override
    public void register (User user) throws RemoteException {
    	if(!users.contains(user)) 
    		users.add(user);
    	else
    		System.out.println("fix this");
    }

	//Make thread-safe
    @Override
	public void unregister(User user) throws RemoteException {
			users.remove(user);
	}
    
}

[Tony Docherty]

Your client's disconnect method should be calling the server's unregister method (ie it should be basically the same as the client's connect method) rather than trying to unregister the server object from the RMI Registry.

[Sven Sylta]

Now I need to register every Client in my Server-class in order to be able to broadcast messages to all clients. So I'm trying to pass "this"-client as an argument to my server-registration-method but it is not working. It worked well just passing a "User" as an argument. Why can't I pass "this" ?

This is the new connect-method in the Client-class:

@Override
    public void connect() {
    	user = Options.INSTANCE.getUser();
    	EventBus.INSTANCE.publish(new Event (Event.Tag.CONNECTED, user));
    	
    		  SecurityManager sm = System.getSecurityManager();
    	      if (sm == null) 
    	         System.setSecurityManager(new SecurityManager());
    	      
    	 try {
        	Registry registry = LocateRegistry.getRegistry("127.0.0.1", 6666);
		     s = (IServer) registry.lookup(Constants.MB_SERVER_NAME);
			
		     IClient client = this;
			s.register(Options.INSTANCE.getUser(), client);
		} catch (RemoteException | NotBoundException e) {
			e.printStackTrace();
		}
    }

This is the new register-method in the server-class:

   //Make thread-safe
    @Override
    public void register (User user, IClient client) throws RemoteException {
    	if(!users.containsKey(user)) 
    		users.put(user, client);
    	else
    		System.out.println("fix this");
    }

The error message:

java.rmi.ServerException: RemoteException occurred in server thread; nested exception is:
java.rmi.UnmarshalException: error unmarshalling arguments; nested exception is:
java.lang.ClassNotFoundException: edu.gu.hajo.mbclient.core.Client
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:353)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)......................
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