11. RMI Hello World Example package message; import java.rmi.*; /* This interfaces defines the exported methods */ public interface RemoteHelloWorld extends Remote { public String sayHello () throws RemoteException(); }

12. package client; import java.rmi.*; import java.rmi.server.*; import message.*; public static class Client { public static void main(String []args) { try{ System.setSecurityManager(new RMISecurityManager()); //Read a system property, specified on command line with -D // to determine host String url = System.getProperty(“myserver”,”rmi:///HELLO”); RemoteHelloWorld server = (RemoteHelloWorld) Naming.lookup(url); String value = server.sayHello(); System.out.println(value); }catch(RemoteException e) { System.err.println(e);} catch(Exception e) { System.err.println(e); System.err.println(“USAGE: java [-Dmyserver=url>]”); } }}

13. % javac HelloWorld.java % rmic -d . server.HelloWorld % rmiregistry & % java HelloWorld package server; import java.rmi.*; import java.rmi.server.*; import message.*; import java.rmi.registry.*; public class HelloWorld extends UnicastRemoteObject implements RemoteHelloWorld { String sayHello() throws RemoteException{ return “Hello World”;} public static void main(String []args) { try{ HelloWorld theObject= new HelloWorld(); Naming.rebind(String(“HELLO”),theObject); System.out.println(“HELLO is now up and running”); }catch(Exception e){ …} } }

15. Policy file grant { permission java.net.SocketPermission “*:1024-65535”, “accept, connect, listen, resolve”; } grant { permission java.lang.RuntimePermission “createSecurityManager”; };

18. Message Package package message; import java.rmi.*; public interface interface MessageReceiver extends Remote { void print (String s) throws RemoteException; } public interface MessageServer extends Remote { static String SERVER_NAME = “MessageServer”; static int FAILURE = -1; static int SUCCESS = 0; void send(String name,String s) throws RemoteException; int register(String name,MessageReceiver m) throws RemoteException; }

19. Server Package package server; import java.util.Enumeration; import java.util.HashTable; import java.rmi.*; import java.rmi.server.*; import java.rmi.registry.*; import message.*; public class Server extends UnicastRemoteObject implements MessageServer { static HashTable receivers = new HashTable(5); public Server() throws RemoteException { super();} public void send(String name, String s) throws RemoteException { for(Enumeration e = receivers.elements(); e.hasMoreElements();) { MessageReceiver m = (MessageReceiver) e.nextElement(); m.print(name + “: “ + s); } }

20. public int register( Strin g name, MessageReceiver m) { int retval = MessageServer.FAILURE; if((name != null) && (m != null)) { if(receivers.get(name) == null) { receivers.put(name,m); System.out.println(“Added “ + name); retval = MessageServer.SUCCESS; }else { System.out.println(“Client not added because “ + name + “ already exists on Server”); } } return retval; } public static void main(String []args) { System.setSecurityManager(new RMISecurityManager()); try { MessageServer server = new Server(); // Bootstrap PRIVATE registry! Registry reg = LocateRegistry.createRegistry( Registry.REGISTRY_PORT); reg.rebind(MessageServer.SERVER_NAME,server); System.out.println(“Server bound and started”); } catch(Exception e) { …} } }

21. Client package package client; import java.awt.*; import java.awt.event.*; import java.rmi.*; import java.rmi,.server.*; import message.*; public class Client extends Frame implements MessageReceiver, ActionListener, WindowListener { TextField tf; TextArea ta; static String name; static MessageServer server; public Client() throws RemoteException { setTitle(name); setLayout(new BorderLayout()); tf = new TextField(30); tf.addActionListener(this); add(“South”,tf); ta = new TextArea(20,20); addWindowListener(new WindowCloser()); UnicastRemoteObject.exportObject(this); // accept remote calls! }

22. public void actionPerformed(ActionEvent ae) { try { server.send(name,tf.getText()); }catch Exception e) { …}} public void print(String s) { ta.append(s+””);} public static void main(String args[]) { if(args.length < 1) { System.out.println(“USAGE: java client.Client NAME”); System.exit(-1); } name = args[0]; System.setSecurityManager(new RMISecurityManager()); try { Client cf = new Client(); cf.pack();cf.show(); server =(MessageServer) Naming.lookup(MessageServer.SERVER_NAME); int s = server.register(args[0],cf); if(s == MessageServer.FAILURE) throw new Exception(“Could not Connect to SERVER”); } catch(Exception e) {… System.exit(-1);} }}