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

@@ -1,9 +1,19 @@
 package com.university.chat.Client;
 
+import com.university.chat.Common.ChatMessage;
+import com.university.chat.Common.FileMessage;
+
+import java.io.ObjectInputStream;
+
 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)
+    private final ObjectInputStream in;
+
+    public ServerListener(ObjectInputStream in) {
+        this.in = in;
+    }
 
     @Override
     public void run() {
@@ -13,6 +23,14 @@ public class ServerListener implements Runnable{
             //   - if it's a FileMessage  -> print that a file was received
             //                               (filename + sender), it's already
             //                               saved to disk by the server.
+            while (true) {
+                Object obj = in.readObject();
+                if (obj instanceof ChatMessage msg) {
+                    System.out.println(msg.getSender() + ": " + msg.getContent());
+                } else if (obj 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

@@ -1,7 +1,18 @@
 package com.university.chat.Client;
 
+import com.university.chat.Common.ChatMessage;
+import com.university.chat.Common.FileMessage;
+import com.university.chat.Common.MessageType;
+
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.net.Socket;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Scanner;
+
 public class chatClient {
-    public static void main() {
+    public static void main(String[] args) {
         // TODO: Connecting to the server
         //  1. Create a socket and connect to the server
         //  2. Create an ObjectOutputStream (out) and ObjectInputStream (in)
@@ -9,6 +20,38 @@ public class chatClient {
         //  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.
+        Scanner scanner = new Scanner(System.in);
+        String username;
+        ObjectOutputStream out;
+        ObjectInputStream in;
+
+        try {
+            Socket socket = new Socket("localhost", 12345);
+
+            out = new ObjectOutputStream(socket.getOutputStream());
+            in = new ObjectInputStream(socket.getInputStream());
+
+            System.out.print("Enter your username: ");
+            username = scanner.nextLine().trim();
+
+            out.writeObject(new ChatMessage(MessageType.LOGIN, username, null, null));
+            out.flush();
+
+            Object response = in.readObject();
+            if (response instanceof ChatMessage loginReply) {
+                System.out.println(loginReply.getContent());
+                if (loginReply.getType() == MessageType.LOGIN_FAILED) {
+                    socket.close();
+                    return;
+                }
+            }
+
+            new Thread(new ServerListener(in)).start();
+
+        } catch (Exception e) {
+            System.out.println("Could not connect to server: " + e.getMessage());
+            return;
+        }
 
         while (true){
             try {
@@ -21,9 +64,51 @@ public class chatClient {
                 //                                     and send it as a FileMessage
                 //   - anything else               -> send a PUBLIC_MESSAGE
                 //   Remember to flush() the output stream after writeObject().
+                String line = scanner.nextLine();
+
+                if (line.startsWith("/msg ")) {
+                    String[] parts = line.substring(5).split(" ", 2);
+                    if (parts.length < 2) {
+                        System.out.println("Usage: /msg <username> <message>");
+                        continue;
+                    }
+                    out.writeObject(new ChatMessage(MessageType.PRIVATE_MESSAGE, username, parts[0], parts[1]));
+                    out.flush();
+
+                } else if (line.equals("/users")) {
+                    out.writeObject(new ChatMessage(MessageType.USER_LIST, username, null, null));
+                    out.flush();
+
+                } else if (line.startsWith("/sendfile ")) {
+                    String[] parts = line.substring(10).split(" ", 2);
+                    if (parts.length < 2) {
+                        System.out.println("Usage: /sendfile <username> <filepath>");
+                        continue;
+                    }
+                    String receiver = parts[0];
+                    Path path = Path.of(parts[1]);
+
+                    if (!Files.exists(path)) {
+                        System.out.println("File not found: " + parts[1]);
+                        continue;
+                    }
+
+                    byte[] data = Files.readAllBytes(path);
+                    String filename = path.getFileName().toString();
+
+                    TransferProgress progress = new TransferProgress(data.length);
+                    progress.update(data.length);
+
+                    out.writeObject(new FileMessage(username, receiver, filename, data));
+                    out.flush();
+
+                } else {
+                    out.writeObject(new ChatMessage(MessageType.PUBLIC_MESSAGE, username, null, line));
+                    out.flush();
+                }
             } catch (Exception e){
                 System.out.println("command failed: " + e.getMessage());
             }
         }
     }
-}
+}

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

@@ -1,15 +1,29 @@
 package com.university.chat.Server;
 
+import java.io.IOException;
+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(12345)) {
 
-        // TODO: In an infinite loop:
+            // TODO: In an infinite loop:
-        //  accept an incoming client connection
+            //  accept an incoming client connection
-        //  make a new thread running ClientSession for each user.
+            //  make a new thread running ClientSession for each user.
+            while (true) {
+                Socket clientSocket = serverSocket.accept();
+                ClientSession session = new ClientSession(clientSocket, userManager);
+                new Thread(session).start();
+            }
+        } catch (IOException e) {
+            System.out.println("Server error: " + e.getMessage());
+        }
     }
-}
+}

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

@@ -2,18 +2,34 @@ 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 final Socket socket;
+    private final UserManager userManager;
+    private ObjectOutputStream out;
+    private ObjectInputStream in;
+
     private String username;
 
     public ClientSession(Socket socket, UserManager userManager) {
         // TODO : Create an ObjectOutputStream from socket.getOutputStream()
         //         and an ObjectInputStream from socket.getInputStream().
+        this.socket = socket;
+        this.userManager = userManager;
+        try {
+            this.out = new ObjectOutputStream(socket.getOutputStream());
+            this.in = new ObjectInputStream(socket.getInputStream());
+        } catch (IOException e) {
+            System.out.println("Failed to open streams: " + e.getMessage());
+        }
     }
 
     @Override
@@ -28,32 +44,81 @@ public class ClientSession implements Runnable {
             //  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.
+            Object first = in.readObject();
+            if (!(first instanceof ChatMessage loginMsg) || loginMsg.getType() != MessageType.LOGIN) {
+                sendMessage(new ChatMessage(MessageType.LOGIN_FAILED, "server", null, "Expected LOGIN message"));
+                socket.close();
+                return;
+            }
+
+            username = loginMsg.getSender();
+
+            if (!userManager.addUser(username, this)) {
+                sendMessage(new ChatMessage(MessageType.LOGIN_FAILED, "server", username, "Username already taken"));
+                socket.close();
+                return;
+            }
+
+            FileManager.createUserFolders(username);
+            sendMessage(new ChatMessage(MessageType.LOGIN_SUCCESS, "server", username, "Welcome, " + username + "!"));
 
             // 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).
+            while (true) {
+                Object obj = in.readObject();
+                if (obj instanceof ChatMessage msg) {
+                    handleChatMessage(msg);
+                } else if (obj 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);
+            }
+            try {
+                socket.close();
+            } catch (IOException ignored) {
+            }
         }
     }
 
+    public synchronized void sendMessage(Object obj) throws IOException {
+        out.writeObject(obj);
+        out.flush();
+    }
 
     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.sendMessage(msg);
+                }
             }
             case PRIVATE_MESSAGE -> {
                 // TODO: Forward this message to the receiver user.
+                ClientSession receiver = userManager.getUser(msg.getReceiver());
+                if (receiver != null) {
+                    receiver.sendMessage(msg);
+                } else {
+                    sendMessage(new ChatMessage(MessageType.PRIVATE_MESSAGE, "server", username,
+                            "User '" + msg.getReceiver() + "' is not online."));
+                }
             }
             case USER_LIST -> {
                 // TODO: Reply to the requester with the list of online users.
+                sendMessage(new ChatMessage(MessageType.USER_LIST, "server", username, userManager.listUsers()));
+            }
+            default -> {
             }
         }
     }
@@ -67,5 +132,9 @@ public class ClientSession implements Runnable {
         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.sendMessage(fileMsg);
+        }
     }
 }