Callback calls 127.0.1.1 instead of real client IP

[Andrea Guarini]

Hi all, I'd like to ask a question.. it may sound easy but I'm stuck with it.
I have successfully implemented a callback architecture in my program, but it works only if the server and client programs are on the same machine. If I load the client on another machine the client can call any rmi method on the server, but when it's time to use a callback method the server tries to connect to 127.0.1.1.
Should I set java.hostname property also on the client? I don't think so, but never say never..

simplified versions of the sources:

  
Client:

//this class is used to connect to the rmi server and offers a callable method, printRemotely(String m)
public class ServerDelegate implements IRemoteListener
{
        //reference to the remote server interface
        private BusinessDelegateInterface BusinessDelegate;

	private ServerDelegate() throws Exception
	{
		Registry registry = LocateRegistry.getRegistry(path, 3232);
		BusinessDelegate = (BusinessDelegateInterface)(registry.lookup("Root"));
                UnicastRemoteObject.exportObject(this);
		BusinessDelegate.addListener(this);
	}

	//this method is called by the server with the callback method
	public void printMessage(String m) throws Exception
	{
		System.out.println(m);
	}
	

        //when the client finishes loading, I call this method to try the callback system
	public void printRemotely(String m) throws Exception
	{
		BusinessDelegate.printRemotely(m);
	}
}

//interface shared between client and server, implemented by client
public interface IRemoteListener extends Remote
{
	public abstract void printMessage(String m) throws Exception;
}

//interface shared between client and server, implemented by server
public interface BusinessDelegateInterface extends Remote
{
	public abstract void addListener(IRemoteListener l) throws Exception;
	public abstract void removeListener(IRemoteListener l) throws Exception;
	public abstract void printRemotely(String m) throws Exception;
}


Server:
public class RmiDelegate extends UnicastRemoteObject implements BusinessDelegateInterface
{
	private Vector<IRemoteListener> listeners = new Vector<IRemoteListener>();

        //this method registers clients on connection
	public void addListener(IRemoteListener listener) throws Exception
        {
		listeners.addElement(listener);
	}

        //this method removes a client reference when the client disconnects
	public void removeListener(IRemoteListener listener) throws Exception 
        {
		listeners.remove(listener);
	}
	
        //this method simply iterates on all the connected clients and calls the remote method printMessage() using callbacks references
	public void printRemotely(String m) throws Exception 
	{
		System.out.println("RmiDelegate.printRemotely()");
		Vector<IRemoteListener> temp = (Vector<IRemoteListener>) listeners.clone();
		for (Enumeration<IRemoteListener> e = temp.elements(); e.hasMoreElements();) 
		{
			IRemoteListener l = (IRemoteListener) e.nextElement();
			try 
			{
				l.printMessage(m);
			} 
			catch (RemoteException e1) 
			{
				removeListener(l);
				e1.printStackTrace();
			}
			catch (Exception e1) 
			{
				e1.printStackTrace();
			}
		}
	}
}
  

Log of the server console:

RmiDelegate.printRemotely()
java.rmi.ConnectException: Connection refused to host: 127.0.1.1; nested exception is:
java.net.ConnectException: Connection refused
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:601)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:198)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:184)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:110)
at Root.Dominio.ServerDelegate_Stub.printMessage(ServerDelegate_Stub.java:55)
at Root.Rmi.RmiDelegate.printRemotely(RmiDelegate.java:116)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:305)
at sun.rmi.transport.Transport$1.run(Transport.java:159)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:519)
at java.net.Socket.connect(Socket.java:469)
at java.net.Socket.<init>(Socket.java:366)
at java.net.Socket.<init>(Socket.java:180)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:595)
... 19 more

Scripts I use to run the server and the clients:
client:
java -Djava.security.policy=security.policy -jar Client.jar

server:
java -Djava.security.policy=security.policy -Djava.rmi.server.hostname=192.168.1.254 -Djava.rmi.server.codebase=file:/home/Server/Client.jar -jar Server.jar

Can somebody figure out what's wrong in my code?
Thanks in advance, Andrea.

[Andrea Guarini]

I should have set the hostname property also on the client...
I thought the UnicastRemoteObject.exportObject told the server everything it needed to call the clients.
If I have a client which runs on dhcp how should I set this property?
Now I'm in a LAN setting, so I simply put the local IP address of my client machine. Should I put the public IP address?

[Mike Peters]

Normally a client also has a name on the network you could use that in the property (e.g. client.local). I hope this helps.

[Borys Zora]

1) host = "192.168...."
or
2) hostName = InetAddress.getByName(host).getHostAddress();

1) System.setProperty("java.rmi.server.hostname", host);
or
2) System.setProperty("java.rmi.server.hostname", hostName);