// Keep the same server implementation as before import java.io.*; import java.net.*; import java.util.*; public class MessageServer { private static final int PORT = 12345; private static Set clientWriters = new HashSet<>(); public static void main(String[] args) { System.out.println("Server running..."); try (ServerSocket serverSocket = new ServerSocket(PORT)) { while (true) { new ClientHandler(serverSocket.accept()).start(); } } catch (IOException e) { System.err.println("Server exception: " + e.getMessage()); } } private static class ClientHandler extends Thread { private Socket socket; private PrintWriter out; private BufferedReader in; public ClientHandler(Socket socket) { this.socket = socket; } public void run() { try { in = new BufferedReader(new InputStreamReader(socket.getInputStream())); out = new PrintWriter(socket.getOutputStream(), true); synchronized (clientWriters) { clientWriters.add(out); } String message; while ((message = in.readLine()) != null) { System.out.println("Received: " + message); broadcast(message); } } catch (IOException e) { System.err.println("Client handler exception: " + e.getMessage()); } finally { try { socket.close(); } catch (IOException e) { System.err.println("Socket close exception: " + e.getMessage()); } synchronized (clientWriters) { clientWriters.remove(out); } } } } private static void broadcast(String message) { synchronized (clientWriters) { for (PrintWriter writer : clientWriters) { writer.println(message); } } } }

import javax.swing.*; import java.awt.event.*; import java.io.*; import java.net.*; import java.util.concurrent.*; public class MessageClient extends javax.swing.JFrame { private javax.swing.JButton sendButton; private javax.swing.JTextArea messageArea; private javax.swing.JTextField messageField; private javax.swing.JPanel mainPanel; private javax.swing.JPanel inputPanel; private javax.swing.JScrollPane scrollPane; private PrintWriter out; private String username; private ExecutorService executorService; public MessageClient() { initComponents(); executorService = Executors.newSingleThreadExecutor(); connectToServer(); } private void initComponents() { mainPanel = new javax.swing.JPanel(); scrollPane = new javax.swing.JScrollPane(); messageArea = new javax.swing.JTextArea(); inputPanel = new javax.swing.JPanel(); messageField = new javax.swing.JTextField(); sendButton = new javax.swing.JButton(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); setTitle("Messaging Client"); mainPanel.setBorder(javax.swing.BorderFactory.createTitledBorder("Messaging Client")); messageArea.setEditable(false); messageArea.setColumns(40); messageArea.setRows(20); scrollPane.setViewportView(messageArea); messageField.setColumns(30); sendButton.setText("Send"); sendButton.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { sendButtonActionPerformed(evt); } }); javax.swing.GroupLayout inputPanelLayout = new javax.swing.GroupLayout(inputPanel); inputPanel.setLayout(inputPanelLayout); inputPanelLayout.setHorizontalGroup( inputPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(inputPanelLayout.createSequentialGroup() .addContainerGap() .addComponent(messageField) .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED) .addComponent(sendButton) .addContainerGap()) ); inputPanelLayout.setVerticalGroup( inputPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(inputPanelLayout.createSequentialGroup() .addContainerGap() .addGroup(inputPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE) .addComponent(messageField, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) .addComponent(sendButton)) .addContainerGap()) ); javax.swing.GroupLayout mainPanelLayout = new javax.swing.GroupLayout(mainPanel); mainPanel.setLayout(mainPanelLayout); mainPanelLayout.setHorizontalGroup( mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(mainPanelLayout.createSequentialGroup() .addContainerGap() .addGroup(mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addComponent(scrollPane) .addComponent(inputPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)) .addContainerGap()) ); mainPanelLayout.setVerticalGroup( mainPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(mainPanelLayout.createSequentialGroup() .addContainerGap() .addComponent(scrollPane) .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED) .addComponent(inputPanel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) .addContainerGap()) ); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addContainerGap() .addComponent(mainPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) .addContainerGap()) ); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addContainerGap() .addComponent(mainPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE) .addContainerGap()) ); pack(); // Get username username = JOptionPane.showInputDialog(this, "Enter your username:"); if (username == null || username.trim().isEmpty()) { username = "Anonymous"; } setTitle("Messaging Client - " + username); // Add enter key listener to message field messageField.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { sendMessage(); } }); } private void connectToServer() { executorService.execute(() -> { try (Socket socket = new Socket("localhost", 12345)) { out = new PrintWriter(socket.getOutputStream(), true); BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream())); String serverMessage; while ((serverMessage = in.readLine()) != null) { String finalMessage = serverMessage; SwingUtilities.invokeLater(() -> messageArea.append(finalMessage + "\n")); } } catch (IOException e) { SwingUtilities.invokeLater(() -> JOptionPane.showMessageDialog(this, "Error connecting to server: " + e.getMessage(), "Connection Error", JOptionPane.ERROR_MESSAGE)); } }); } private void sendMessage() { String message = messageField.getText(); if (!message.trim().isEmpty()) { out.println(username + ": " + message); messageField.setText(""); } } private void sendButtonActionPerformed(java.awt.event.ActionEvent evt) { sendMessage(); } public static void main(String args[]) { java.awt.EventQueue.invokeLater(() -> { new MessageClient().setVisible(true); }); } } To use the drag-and-drop design in NetBeans: 1. Create a new Java Application project in NetBeans 2. Right-click on the project and select "New" → "JFrame Form" 3. Name it "MessageClient" (this will create both .java and .form files) 4. Open the form in Design view 5. Drag and drop components from the Palette to build your UI: - Add a JPanel as the main container - Add a JScrollPane with a JTextArea for messages - Add another JPanel with a JTextField and JButton for input 6. Set properties for each component in the Properties window 7. The .form file will be automatically generated 8. Add your networking code to the .java file as shown above The provided code includes both the visual form definition and the Java implementation that works with it.