src/main/java/com/university/chat/Client/ServerListener.java

@@ -1,20 +1,40 @@
 package com.university.chat.Client;
 
-public class ServerListener implements Runnable{
-    // TODO: store the ObjectInputStream from the user socket
-    //          (this should be the same input stream the
-    //           chatClient created when connecting)
+import com.university.chat.Common.ChatMessage;
+import com.university.chat.Common.FileMessage;
+
+import java.io.ObjectInputStream;
+
+public class ServerListener implements Runnable {
+
+    private ObjectInputStream in;
+
+    public ServerListener(ObjectInputStream in) {
+        this.in = in;
+    }
 
     @Override
     public void run() {
         try {
-            // TODO: In an infinite loop read objects from the server
-            //   - if it's a ChatMessage  -> print "<sender>: <content>"
-            //   - if it's a FileMessage  -> print that a file was received
-            //                               (filename + sender), it's already
-            //                               saved to disk by the server.
-        } catch (Exception e){
+            while (true) {
+                Object object = in.readObject();
+
+                if (object instanceof ChatMessage msg) {
+                    System.out.println(msg.getSender() + ": " + msg.getContent());
+                }
+
+                if (object instanceof FileMessage fileMsg) {
+                    System.out.println(
+                            "File received: " +
+                                    fileMsg.getFilename() +
+                                    " from " +
+                                    fileMsg.getSender()
+                    );
+                }
+            }
+
+        } catch (Exception e) {
             System.out.println("Disconnected from server");
         }
     }
-}
+}

src/main/java/com/university/chat/Client/chatClient.java

@@ -1,29 +1,106 @@
 package com.university.chat.Client;
 
-public class chatClient {
-    public static void main() {
-        // TODO: Connecting to the server
-        //  1. Create a socket and connect to the server
-        //  2. Create an ObjectOutputStream (out) and ObjectInputStream (in)
-        //      from the socket's streams — output FIRST, then input.
-        //  2. Get the username, and send a LOGIN ChatMessage with that username
-        //  3. Start a new Thread running a ServerListener(in) so incoming
-        //      messages are handled concurrently.
+import com.university.chat.Common.ChatMessage;
+import com.university.chat.Common.FileMessage;
+import com.university.chat.Common.MessageType;
 
-        while (true){
-            try {
-                // TODO: Program loop — read a line from the console and act on it:
-                //   - "/msg <user> <text>"        -> build & send a PRIVATE_MESSAGE
-                //   - "/users"                    -> build & send a USER_LIST request
-                //   - "/sendfile <user> <path>"   -> read the file into a byte[]
-                //                                     (you can use TransferProgress
-                //                                     to show progress)
-                //                                     and send it as a FileMessage
-                //   - anything else               -> send a PUBLIC_MESSAGE
-                //   Remember to flush() the output stream after writeObject().
-            } catch (Exception e){
-                System.out.println("command failed: " + e.getMessage());
+import java.io.File;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.net.Socket;
+import java.nio.file.Files;
+import java.util.Scanner;
+
+public class chatClient {
+
+    public static void main(String[] args) {
+        try {
+            Socket socket = new Socket("localhost", 5000);
+
+            ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
+            ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
+
+            Scanner scanner = new Scanner(System.in);
+
+            System.out.print("Enter username: ");
+            String username = scanner.nextLine();
+
+            ChatMessage loginMessage = new ChatMessage(
+                    MessageType.LOGIN,
+                    username,
+                    null,
+                    ""
+            );
+
+            out.writeObject(loginMessage);
+            out.flush();
+
+            new Thread(new ServerListener(in)).start();
+
+            while (true) {
+                try {
+                    String line = scanner.nextLine();
+
+                    if (line.startsWith("/msg ")) {
+                        String[] parts = line.split(" ", 3);
+
+                        ChatMessage privateMessage = new ChatMessage(
+                                MessageType.PRIVATE_MESSAGE,
+                                username,
+                                parts[1],
+                                parts[2]
+                        );
+
+                        out.writeObject(privateMessage);
+                    }
+
+                    else if (line.equals("/users")) {
+                        ChatMessage userListMessage = new ChatMessage(
+                                MessageType.USER_LIST,
+                                username,
+                                null,
+                                ""
+                        );
+
+                        out.writeObject(userListMessage);
+                    }
+
+                    else if (line.startsWith("/sendfile ")) {
+                        String[] parts = line.split(" ", 3);
+
+                        File file = new File(parts[2]);
+                        byte[] data = Files.readAllBytes(file.toPath());
+
+                        FileMessage fileMessage = new FileMessage(
+                                username,
+                                parts[1],
+                                file.getName(),
+                                data
+                        );
+
+                        out.writeObject(fileMessage);
+                    }
+
+                    else {
+                        ChatMessage publicMessage = new ChatMessage(
+                                MessageType.PUBLIC_MESSAGE,
+                                username,
+                                null,
+                                line
+                        );
+
+                        out.writeObject(publicMessage);
+                    }
+
+                    out.flush();
+
+                } catch (Exception e) {
+                    System.out.println("command failed: " + e.getMessage());
+                }
             }
+
+        } catch (Exception e) {
+            System.out.println("Could not connect to server");
         }
     }
-}
+}

src/main/java/com/university/chat/Server/ChatServer.java

@@ -1,15 +1,24 @@
 package com.university.chat.Server;
 
+import java.net.ServerSocket;
+import java.net.Socket;
+
 public class ChatServer {
-    // TODO: declare a single shared UserManager instance (static final)
-    //         This MUST be shared by all ClientSession threads so that
-    //         broadcasting and private messaging work correctly.
+
+    private static final UserManager userManager = new UserManager();
 
     public static void main(String[] args) {
-        // TODO: Create a ServerSocket
+        try {
+            ServerSocket serverSocket = new ServerSocket(5000);
 
-        // TODO: In an infinite loop:
-        //  accept an incoming client connection
-        //  make a new thread running ClientSession for each user.
+            while (true) {
+                Socket socket = serverSocket.accept();
+                ClientSession session = new ClientSession(socket, userManager);
+                new Thread(session).start();
+            }
+
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
     }
-}
+}

src/main/java/com/university/chat/Server/ClientSession.java

@@ -2,70 +2,160 @@ package com.university.chat.Server;
 
 import com.university.chat.Common.ChatMessage;
 import com.university.chat.Common.FileMessage;
+import com.university.chat.Common.MessageType;
 
 import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.net.Socket;
 import java.nio.file.Files;
 
 public class ClientSession implements Runnable {
 
     private String username;
+    private Socket socket;
+    private UserManager userManager;
+    private ObjectInputStream in;
+    private ObjectOutputStream out;
 
     public ClientSession(Socket socket, UserManager userManager) {
-        // TODO : Create an ObjectOutputStream from socket.getOutputStream()
-        //         and an ObjectInputStream from socket.getInputStream().
+        try {
+            this.socket = socket;
+            this.userManager = userManager;
+
+            out = new ObjectOutputStream(socket.getOutputStream());
+            in = new ObjectInputStream(socket.getInputStream());
+
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
     }
 
     @Override
     public void run() {
         try {
+            Object firstObject = in.readObject();
 
-            // TODO: Welcome the user (login step)
-            //  1. Read the first object sent by the client.
-            //  2. Check it's a ChatMessage with type LOGIN.
-            //  3. Extract the username.
-            //  4. Try to register the user via userManager.addUser(...).
-            //  5. If the username is taken, send back LOGIN_FAILED and close the socket.
-            //  6. Otherwise, create the user's folders with FileManager.createUserFolders(...)
-            //      and send back LOGIN_SUCCESS.
+            if (!(firstObject instanceof ChatMessage loginMessage)) {
+                socket.close();
+                return;
+            }
 
-            // TODO: Main message loop
-            //   In a loop, call in.readObject(), you can separate messages by their type:
-            //     - if it's a ChatMessage      -> call handleChatMessage(msg)
-            //     - if it's a FileMessage      -> call handleFileMessage(fileMsg)
-            //   Keep looping until the connection is closed (an exception will be thrown).
+            if (loginMessage.getType() != MessageType.LOGIN) {
+                socket.close();
+                return;
+            }
+
+            username = loginMessage.getSender();
+
+            boolean added = userManager.addUser(username, this);
+
+            if (!added) {
+                ChatMessage failedMessage = new ChatMessage(
+                        MessageType.LOGIN_FAILED,
+                        "SERVER",
+                        username,
+                        "Username already exists"
+                );
+
+                send(failedMessage);
+                socket.close();
+                return;
+            }
+
+            FileManager.createUserFolders(username);
+
+            ChatMessage successMessage = new ChatMessage(
+                    MessageType.LOGIN_SUCCESS,
+                    "SERVER",
+                    username,
+                    "Login successful"
+            );
+
+            send(successMessage);
+
+            while (true) {
+                Object object = in.readObject();
+
+                if (object instanceof ChatMessage msg) {
+                    handleChatMessage(msg);
+                }
+
+                if (object instanceof FileMessage fileMsg) {
+                    handleFileMessage(fileMsg);
+                }
+            }
 
         } catch (Exception e) {
             System.out.println("Disconnected: " + username);
         } finally {
-            // TODO: Remove the user from UserManager so they no longer
-            //        receive broadcasts or appear in users list
+            if (username != null) {
+                userManager.removeUser(username);
+            }
         }
     }
 
-
     private void handleChatMessage(ChatMessage msg) throws IOException {
         switch (msg.getType()) {
+
             case PUBLIC_MESSAGE -> {
-                // TODO: Broadcast this message to every connected client.
+                for (ClientSession session : userManager.getAllSessions()) {
+                    session.send(msg);
+                }
             }
+
             case PRIVATE_MESSAGE -> {
-                // TODO: Forward this message to the receiver user.
+                ClientSession receiver = userManager.getUser(msg.getReceiver());
+
+                if (receiver != null) {
+                    receiver.send(msg);
+                }
             }
+
             case USER_LIST -> {
-                // TODO: Reply to the requester with the list of online users.
+                ChatMessage userListMessage = new ChatMessage(
+                        MessageType.USER_LIST,
+                        "SERVER",
+                        username,
+                        userManager.listUsers()
+                );
+
+                send(userListMessage);
+            }
+
+            default -> {
             }
         }
     }
 
     private void handleFileMessage(FileMessage fileMsg) throws IOException {
-        // Storing the file
-        var sentPath = FileManager.getSentPath(fileMsg.getSender(), fileMsg.getFilename());
-        var recvPath = FileManager.getReceivedPath(fileMsg.getReceiver(), fileMsg.getFilename());
+        var sentPath = FileManager.getSentPath(
+                fileMsg.getSender(),
+                fileMsg.getFilename()
+        );
+
+        var recvPath = FileManager.getReceivedPath(
+                fileMsg.getReceiver(),
+                fileMsg.getFilename()
+        );
 
         Files.write(sentPath, fileMsg.getData());
         Files.write(recvPath, fileMsg.getData());
 
-        // TODO: Forward the received file-message to the destination user.
+        ClientSession receiver = userManager.getUser(fileMsg.getReceiver());
+
+        if (receiver != null) {
+            receiver.send(fileMsg);
+        }
+    }
+
+    public void send(ChatMessage msg) throws IOException {
+        out.writeObject(msg);
+        out.flush();
+    }
+
+    public void send(FileMessage msg) throws IOException {
+        out.writeObject(msg);
+        out.flush();
     }
 }