Overriding the Default Ports

All code modifications below are indicated in red.
If the registry is running on a port other than the default, for example 21001, you need to specify the port number:

in the name handed to the URL-based methods of the java.rmi.Naming class when making calls to the registry
on the command line when you start the rmiregistry.

For Unix:

For Dos:

For example, if we were to modify the port in the Hello World example:

import java.rmi.Naming;

import java.rmi.RemoteException;

import java.rmi.RMISecurityManager;

import java.rmi.server.UnicastRemoteObject;

public class HelloImpl extends UnicastRemoteObject
implements Hello {

public HelloImpl() throws RemoteException { }

   public String sayHello() {
            return "Port 2001: Hello RMI world!";
        }

public static void main(String args[]) {

            try {
                HelloImpl obj = new HelloImpl();
                Naming.rebind("//lysander.cs.ucsb.edu:21001/HelloServer", obj);
            } catch (Exception e) {
                 System.out.println("HelloImpl err: " + e.getMessage());
                 e.printStackTrace();
            }
        }
    }

The HelloClient's Naming.lookup() arguments also must reflect this port:

import java.rmi.Naming;
import java.rmi.RemoteException;

public class HelloClient {

public static void main(String arg[]) {

String message = "blank";
Hello obj = null;

                try {
                    obj = (Hello) Naming.lookup("rmi://" +
                          "lysander.cs.ucsb.edu:21001" +
                          "/HelloServer");
                    System.out.println(obj.sayHello());
                } catch (Exception e) {
                    System.out.println("HelloClient exception: " + e.getMessage());
                    e.printStackTrace();
                }
            }
        }