complete server-side classes

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

@@ -1,15 +1,34 @@
 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
+    private static final UserManager userManager = new UserManager();
-    //         broadcasting and private messaging work correctly.
 
     public static void main(String[] args) {
-        // TODO: Create a ServerSocket
 
-        // TODO: In an infinite loop:
+        final int port = 12345;
-        //  accept an incoming client connection
+        System.out.println("chat server starting on port "+port);
-        //  make a new thread running ClientSession for each user.
+        try (ServerSocket serverSocket = new ServerSocket(port)) {
+            System.out.println("server is listening...");
+
+            while (true)
+            {
+                Socket clientSocket = serverSocket.accept();
+                System.out.println("new client connected from "+clientSocket.getInetAddress());
+
+                ClientSession session = new ClientSession(clientSocket, userManager);
+                Thread clientThread = new Thread(session);
+                clientThread.start();
+            }
+        } catch (IOException e)
+        {
+            System.err.println(e.getMessage());
+            e.printStackTrace();
+        }
+
     }
 }

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

@@ -2,44 +2,118 @@ 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 final Socket socket;
+    private final UserManager userManager;
+    private ObjectInputStream in;
+    private ObjectOutputStream out;
+
 
     public ClientSession(Socket socket, UserManager userManager) {
-        // TODO : Create an ObjectOutputStream from socket.getOutputStream()
+        this.socket = socket;
-        //         and an ObjectInputStream from socket.getInputStream().
+        this.userManager = userManager;
+        try
+        {
+            out = new ObjectOutputStream(socket.getOutputStream());
+            out.flush();
+            in = new ObjectInputStream(socket.getInputStream());
+        } catch (IOException e)
+        {
+            e.printStackTrace();
+        }
     }
 
     @Override
     public void run() {
         try {
-
+            //  Welcome the user (login step)
-            // TODO: Welcome the user (login step)
             //  1. Read the first object sent by the client.
+            Object obj = in.readObject();
+
             //  2. Check it's a ChatMessage with type LOGIN.
+            if (!(obj instanceof ChatMessage))
+            {
+                socket.close();
+                return;
+            }
+            ChatMessage loginMsg = (ChatMessage) obj;
+            if (loginMsg.getType() != MessageType.LOGIN)
+            {
+                out.writeObject(new ChatMessage(MessageType.LOGIN_FAILED, "Server", null, "Invalid login request"));
+                out.flush();
+                socket.close();
+                return;
+            }
+
             //  3. Extract the username.
+            String requestedUser = loginMsg.getContent();
+
             //  4. Try to register the user via userManager.addUser(...).
+            boolean success = userManager.addUser(requestedUser, this);
+
             //  5. If the username is taken, send back LOGIN_FAILED and close the socket.
+            if (!success)
+            {
+                out.writeObject(new ChatMessage(MessageType.LOGIN_FAILED, "Server", null, "Username is already taken"));
+                out.flush();
+                socket.close();
+                return;
+            }
+
             //  6. Otherwise, create the user's folders with FileManager.createUserFolders(...)
             //      and send back LOGIN_SUCCESS.
+            this.username = requestedUser;
+            out.writeObject(new ChatMessage(MessageType.LOGIN_SUCCESS, "Server", null, "Welcome "+username));
+            out.flush();
+            System.out.println("User logged in: "+username);
 
-            // TODO: Main message loop
+            //  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 received = in.readObject();
+                if (received instanceof ChatMessage)
+                {
+                    handleChatMessage((ChatMessage) received);
+                } else if (received instanceof FileMessage)
+                {
+                    handleFileMessage((FileMessage) received);
+                }
+            }
 
         } catch (Exception e) {
             System.out.println("Disconnected: " + username);
         } finally {
-            // TODO: Remove the user from UserManager so they no longer
+            //  Remove the user from UserManager so they no longer
             //        receive broadcasts or appear in users list
+            if (username != null)
+            {
+                userManager.removeUser(username);
+                System.out.println("User removed: "+username);
+            }
+            try
+            {
+                if (socket != null && !socket.isClosed())
+                {
+                    socket.close();
+                }
+            } catch (IOException e)
+            {
+                e.printStackTrace();
+            }
         }
     }
 
@@ -47,13 +121,36 @@ public class ClientSession implements Runnable {
     private void handleChatMessage(ChatMessage msg) throws IOException {
         switch (msg.getType()) {
             case PUBLIC_MESSAGE -> {
-                // TODO: Broadcast this message to every connected client.
+                //  Broadcast this message to every connected client.
+                for (ClientSession session : userManager.getAllSessions())
+                {
+                    if (session != this)
+                    {
+                        session.out.writeObject(msg);
+                        session.out.flush();
+                    }
+                }
             }
             case PRIVATE_MESSAGE -> {
-                // TODO: Forward this message to the receiver user.
+                //  Forward this message to the receiver user.
+                String receiver = msg.getReceiver();
+                ClientSession target = userManager.getUser(receiver);
+                if (target != null)
+                {
+                    target.out.writeObject(msg);
+                    target.out.flush();
+                } else {
+                    out.writeObject(new ChatMessage(MessageType.PRIVATE_MESSAGE, "Server", null,
+                            "User " + receiver + " is not online."));
+                    out.flush();
+                }
             }
             case USER_LIST -> {
-                // TODO: Reply to the requester with the list of online users.
+                //  Reply to the requester with the list of online users.
+                String list = userManager.listUsers();
+                ChatMessage listMsg = new ChatMessage(MessageType.USER_LIST, "Server", null, list);
+                out.writeObject(listMsg);
+                out.flush();
             }
         }
     }
@@ -66,6 +163,16 @@ public class ClientSession implements Runnable {
         Files.write(sentPath, fileMsg.getData());
         Files.write(recvPath, fileMsg.getData());
 
-        // TODO: Forward the received file-message to the destination user.
+        //  Forward the received file-message to the destination user.
+        ClientSession receiver = userManager.getUser(fileMsg.getReceiver());
+        if (receiver != null)
+        {
+            receiver.out.writeObject(fileMsg);
+            receiver.out.flush();
+        } else
+        {
+            out.writeObject(new ChatMessage(MessageType.PRIVATE_MESSAGE, "Server", null, "Cannot send file; user "+fileMsg.getReceiver()+" is offline"));
+            out.flush();
+        }
     }
 }