RMI example in Java 2 Platform SE 5.0

RMI stands for Remote Method Invocation. As of the J2SE 5.0 release, stub classes for remote objects no longer need to be pregenerated using the rmic stub compiler, unless the remote object needs to support clients running in pre-5.0 VMs. So because I'm testing RMI with the JDK 5.0, I won't compile stub classes.

First define interface:

public interface Hello extends java.rmi.Remote {
    String sayHello() throws java.rmi.RemoteException;
}

Server class:

import java.rmi.*;
import java.rmi.registry.*;
import java.rmi.server.*;

public class Server implements Hello {
    public Server() {}
    public String sayHello() {
        return "Hello, world!";
    }
    public static void main(String args[]) {
        System.setSecurityManager(new RMISecurityManager());
        final Server obj = new Server();
        try {                               // 0 - anonymous TCP port ↓
            Hello stub = (Hello)UnicastRemoteObject.exportObject(obj, 0);
            // Bind the remote object's stub in the registry
            Registry registry = LocateRegistry.createRegistry(1099);
            registry.rebind("Hello", stub);
            for(int i = 0; i < registry.list().length; i++)
                System.out.println(registry.list()[i]);
            System.err.println("Server ready");
        } catch (Exception e) {
            e.printStackTrace();
        }
        // Needed for windows98 se, optional for windows xp
        new Thread() {
            public void run() {
                Server s = obj;
                while(true);
            }
        }.start();
    }
}

Client class:

import java.rmi.registry.*;
import java.rmi.*;

public class Client {
    private Client() {}
    public static void main(String[] args) {
        String host = (args.length < 1) ? null : args[0];
        try {
            Registry registry = LocateRegistry.getRegistry(host);
            Hello stub = (Hello)registry.lookup("Hello");
            // or Hello stub = (Hello)Naming.lookup("rmi://" + host + "/Hello");
            String response = stub.sayHello();
            System.out.println("response: " + response);
        } catch (Exception e) {
            System.err.println("Client exception: " + e.toString());
            e.printStackTrace();
        }
    }
}

Create file policy.txt with this text inside:

grant {
    // Allow everything for now
    permission java.security.AllPermission;
};

On the server computer run:

java -Djava.security.policy=policy.txt Server

On the client computer run:

java Client 192.168.0.3

Note: substitute ip address of your own or write hostname instead of ip address.

Feel free to post your questions or comments.