1. Client.java
2. Hello.java
3. Server.java

import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;

/**
 * RMI Client
 * 
 * @author Sara Sprenkle
 */
public class Client {

    public static void main(String[] args) {
	String host = (args.length < 1) ? "localhost" : args[0];
	try {
	    Registry registry = LocateRegistry.getRegistry(host, 8888);
	    Hello stub = (Hello) registry.lookup("Hello");
	    String response = stub.sayHello();
	    System.out.println("response: " + response);
	    
	    int[] results = stub.sumDifference(30, 40);
	    System.out.println("sumDifference response: " + results[0] + "\n" + results[1]);
	} catch (Exception e) {
	    System.err.println("Client exception: " + e.toString());
	}
    }
}

import java.rmi.Remote;
import java.rmi.RemoteException;

/**
 * Interface for the server's available methods
 * 
 * @author Sara Sprenkle
 */
public interface Hello extends Remote {
    String sayHello() throws RemoteException;

    int[] sumDifference(int x, int y) throws RemoteException;
}

import java.rmi.registry.Registry;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.UnicastRemoteObject;

/**
 * RMI Server
 * 
 * @author Sara Sprenkle
 */
public class Server implements Hello {
    public Server() {
    }

    /**
     * @return "Hello, world!"
     */
    public String sayHello() {
	return "Hello, world!";
    }
    
    /**
     * @return the sum and difference of x and y
     */
    public int[] sumDifference(int x, int y) {
	int[] results = new int[2];
	results[0] = x + y;
	results[1] = y - x;
	return results;
    }
    
    public static void main(String args[]) {
	try {
	    Server obj = new Server();
	    Hello stub = (Hello) UnicastRemoteObject.exportObject(obj, 0);
	    Registry registry = LocateRegistry.createRegistry(8888);
	    registry.bind("Hello", stub);
	} catch (Exception e) {
	    System.err.println("Server exception: " + e.toString());
	}
    }
}