task 5 started.

week3_TinsaeGhilay/Task 5/src/client/Client.java

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+package client;
+
+import java.rmi.server.UnicastRemoteObject;
+import java.rmi.RemoteException;
+import java.rmi.registry.LocateRegistry;
+import java.rmi.registry.Registry;
+import java.util.Scanner;
+import common.ClientInterface;
+import common.ServerInterface;
+
+public class Client extends UnicastRemoteObject implements ClientInterface {
+    private String clientId;
+    private ServerInterface server;
+
+    protected Client(String clientId, ServerInterface server) throws RemoteException {
+        super();
+        this.clientId = clientId;
+        this.server = server;
+        server.registerClient(clientId, this);
+    }
+
+    public void sendMessage(String toId, String message) throws RemoteException {
+        server.sendMessage(clientId, toId, message);
+    }
+
+    public void blockClient(String blockedId) throws RemoteException {
+        server.blockClient(clientId, blockedId);
+    }
+
+    @Override
+    public void receiveMessage(String fromId, String message) throws RemoteException {
+        System.out.println("[" + fromId + "]: " + message);
+    }
+
+    // entry point
+    public static void main(String[] args) {
+        try (Scanner scanner = new Scanner(System.in)) {
+            // get client ID and server info
+            System.out.print("Enter your client ID: ");
+            String clientId = scanner.nextLine();
+
+            // get recipient ID
+            System.out.print("Enter recipient ID: ");
+            String toId = scanner.nextLine();
+
+            Registry registry = LocateRegistry.getRegistry("localhost", 1099);
+            ServerInterface server = (ServerInterface) registry.lookup("ChatServer");
+
+            Client client = new Client(clientId, server);
+
+            System.out.print("You can start chatting now. Type your messages below: Type exit to log out\n");
+
+            while (true) {
+                String msg = scanner.nextLine();
+                if (msg.equalsIgnoreCase("exit")) {
+                    System.out.println("Logging out...");
+                    break;
+                }
+                client.sendMessage(toId, msg);
+            }
+        } catch (Exception e) {
+            System.err.println("Client exception: " + e.getMessage());
+        }
+    }
+
+}

week3_TinsaeGhilay/Task 5/src/common/ClientInterface.java

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+package common;
+
+/**
+ * ClientInterface interface
+ * 
+ * @author Tinsae Ghilay
+ *
+ */
+import java.rmi.Remote;
+import java.rmi.RemoteException;
+
+public interface ClientInterface extends Remote {
+
+    void receiveMessage(String fromId, String message) throws RemoteException;
+
+}

week3_TinsaeGhilay/Task 5/src/common/ServerInterface.java

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+package common;
+
+/**
+ * ClientInterface interface
+ * 
+ * @author Tinsae Ghilay
+ *
+ */
+import java.rmi.Remote;
+import java.rmi.RemoteException;
+import java.util.List;
+
+public interface ServerInterface extends Remote {
+
+    void registerClient(String clientId, ClientInterface client) throws RemoteException;
+
+    void sendMessage(String fromId, String toId, String message) throws RemoteException;
+
+    void blockClient(String clientId, String blockedId) throws RemoteException;
+
+    List<String> getOfflineMessages(String clientId) throws RemoteException;
+
+}

week3_TinsaeGhilay/Task 5/src/server/Server.java

@@ -0,0 +1,69 @@
+package server;
+
+import java.rmi.server.UnicastRemoteObject;
+import java.rmi.RemoteException;
+import java.util.*;
+import java.rmi.registry.LocateRegistry;
+import java.rmi.registry.Registry;
+// import interfaces
+import common.ClientInterface;
+import common.ServerInterface;
+
+public class Server extends UnicastRemoteObject implements ServerInterface {
+    private Map<String, ClientInterface> onlineClients = new HashMap<>();
+    private Map<String, List<String>> offlineMessages = new HashMap<>();
+    private Map<String, Set<String>> blockedClients = new HashMap<>();
+
+    protected Server() throws RemoteException {
+        super();
+    }
+
+    @Override
+    public synchronized void registerClient(String clientId, ClientInterface client) throws RemoteException {
+        onlineClients.put(clientId, client);
+        blockedClients.putIfAbsent(clientId, new HashSet<>());
+
+        // Send any offline messages
+        List<String> messages = offlineMessages.getOrDefault(clientId, new ArrayList<>());
+        for (String msg : messages) {
+            client.receiveMessage("Offline", msg);
+        }
+        offlineMessages.remove(clientId);
+    }
+
+    @Override
+    public synchronized void sendMessage(String fromId, String toId, String message) throws RemoteException {
+        // Check if recipient blocked sender
+        Set<String> blocked = blockedClients.getOrDefault(toId, Collections.emptySet());
+        if (blocked.contains(fromId))
+            return;
+
+        ClientInterface recipient = onlineClients.get(toId);
+        if (recipient != null) {
+            recipient.receiveMessage(fromId, message);
+        } else {
+            // Store message for offline delivery
+            offlineMessages.putIfAbsent(toId, new ArrayList<>());
+            offlineMessages.get(toId).add(fromId + ": " + message);
+        }
+    }
+
+    @Override
+    public synchronized void blockClient(String clientId, String blockedId) throws RemoteException {
+        blockedClients.putIfAbsent(clientId, new HashSet<>());
+        blockedClients.get(clientId).add(blockedId);
+    }
+
+    @Override
+    public synchronized List<String> getOfflineMessages(String clientId) throws RemoteException {
+        return offlineMessages.getOrDefault(clientId, Collections.emptyList());
+    }
+
+    // entry point
+    public static void main(String[] args) throws Exception {
+        Server server = new Server();
+        Registry registry = LocateRegistry.createRegistry(1099);
+        registry.rebind("ChatServer", server);
+        System.out.println("Chat server running...");
+    }
+}