Tirei interações com o socket e regras de negócio da interface e juntei tudo numa classe controladora.

src/br/edu/ufsj/sms/GUI/ChatWindow.java

@@ -57,14 +57,6 @@ public class ChatWindow extends javax.swing.JDialog {
         jPanel1.setLayout(new java.awt.BorderLayout());
         jTextArea1.setColumns(20);
         jTextArea1.setRows(5);
-        jTextArea1.addKeyListener(new java.awt.event.KeyAdapter() {
-            @Override
-            public void keyTyped(java.awt.event.KeyEvent evt) {
-                if (evt.getKeyChar() == '\n') {
-                    sendMessage();
-                }
-            }
-        });
         jButton1.setText("Send");
 
         jScrollPane1.setViewportView(jEditorPane1);
@@ -73,9 +65,6 @@ public class ChatWindow extends javax.swing.JDialog {
 
         jPanel1.add(jScrollPane2, java.awt.BorderLayout.CENTER);
         jPanel2.setLayout(new java.awt.FlowLayout(java.awt.FlowLayout.RIGHT));
-        jButton1.addActionListener((java.awt.event.ActionEvent evt) -> {
-            sendMessage();
-        });
         jPanel2.add(jButton1);
         jPanel1.add(jPanel2, java.awt.BorderLayout.PAGE_END);
         jSplitPane1.setRightComponent(jPanel1);
@@ -83,15 +72,21 @@ public class ChatWindow extends javax.swing.JDialog {
         pack();
     }
 
-    private void sendMessage() {
-        if (jTextArea1.getText().trim().length() == 0) {
-            return;
-        }
-        mainWindow.sendChatMessage(jTextArea1.getText());
-        jTextArea1.setText("");
-    }
-
     public void receiveChatMessage(String message) {
         jEditorPane1.setText(message + jEditorPane1.getText());
     }
+
+    public javax.swing.JButton getButton(){
+        return this.jButton1;
+    }
+    
+    public javax.swing.JTextArea getJTextArea(){
+        return this.jTextArea1; 
+    }
+
+    public String getText(){
+        String text = jTextArea1.getText();
+        jTextArea1.setText("");
+        return text;
+    }
 }

src/br/edu/ufsj/sms/GUI/MainWindow.java

@@ -5,6 +5,7 @@
  */
 package br.edu.ufsj.sms.GUI;
 
+import br.edu.ufsj.sms.GUI.MenuBar;
 import br.edu.ufsj.sms.control.AlarmClock;
 import br.edu.ufsj.sms.control.ImageTransformation;
 import br.edu.ufsj.sms.control.ScreenShot;
@@ -36,26 +37,20 @@ public class MainWindow extends javax.swing.JFrame {
     private javax.swing.JPanel statusPanel;
     private javax.swing.JTabbedPane tabbedPane;
     private ChatWindow chatWindow;
-
+    private MenuBar menuBar;
-    private Socket socket;
-    private AlarmClock alarmClock;
-    private Timer timer;
-    public final static int TIME = 1000;
 
     private String name;
     private int port;
 
-    private float compressRatio;
+    public MainWindow(String name, int port) {
-
-    public MainWindow(String name, int port) throws UnknownHostException {
         this.name = name;
         this.port = port;
-        this.compressRatio = 0.5f;
         this.initComponents();
     }
 
-    private void initComponents() throws UnknownHostException {
+    private void initComponents() {
-        this.setJMenuBar(new MenuBar(this));
+        this.menuBar = new MenuBar(this);
+        this.setJMenuBar(this.menuBar);
         this.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
         this.setTitle("Share My Sheet");
 
@@ -74,14 +69,18 @@ public class MainWindow extends javax.swing.JFrame {
 
         this.pack();
 
-        this.socket = new Socket(this);
-        this.timer = new Timer();
         this.chatWindow = new ChatWindow(this);
-
-        this.socket.start();
         this.setSize(new java.awt.Dimension(1024, 768));
     }
 
+    public ChatWindow getChatWindow(){
+        return this.chatWindow;
+    }
+
+    public MenuBar getSMSMenuBar(){
+        return this.menuBar;
+    }
+
     public void showChatWindow() {
         this.chatWindow.setVisible(true);
     }
@@ -90,16 +89,6 @@ public class MainWindow extends javax.swing.JFrame {
 
     }
 
-    public void shareMySheet(boolean status) {
-        if (status) {
-            this.timer = new Timer();
-            this.alarmClock = new AlarmClock(this);
-            this.timer.scheduleAtFixedRate(this.alarmClock, 0, MainWindow.TIME);
-        } else {
-            this.timer.cancel();
-        }
-    }
-
     public void closeCurrentTab() {
         tabbedPane.remove(tabbedPane.getSelectedIndex());
     }
@@ -110,37 +99,7 @@ public class MainWindow extends javax.swing.JFrame {
         this.dispose();
         System.exit(0);
     }
-
+       
-    public void sendChatMessage(String text) {
-        ChatMessage message = new ChatMessage(this.name, text);
-        try {
-            this.socket.send(message.toByteArray());
-        } catch (IOException ex) {
-            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
-        }
-    }
-
-    public void sendScreenCastMessage() {
-        byte[] msg = null;
-        try {
-            BufferedImage image = ScreenShot.takeAShot();
-            BufferedImage rescaled = ImageTransformation.resize(image, 1024, 768);
-            byte[] byteImage = ImageTransformation.compress(rescaled, compressRatio);
-            ScreenCastMessage message = new ScreenCastMessage(this.name, byteImage);
-            msg = message.toByteArray();
-        } catch (AWTException | IOException ex) {
-            Logger.getLogger(AlarmClock.class.getName()).log(Level.SEVERE, null, ex);
-        }
-        if (msg != null) {
-            try {
-                this.socket.send(msg);
-            } catch (IOException ex) {
-                Logger.getLogger(AlarmClock.class.getName()).log(Level.SEVERE, null, ex);
-                this.compressRatio -= 0.05f;
-            }
-        }
-    }
-
     public void receiveScreenCastMessage(ScreenCastMessage message) {
         ByteArrayInputStream bais = new ByteArrayInputStream(message.getImageByte());
         BufferedImage image;

src/br/edu/ufsj/sms/GUI/MenuBar.java

@@ -55,13 +55,11 @@ public class MenuBar extends JMenuBar {
 
         editMenu.setText("Edit");
         shareMySheetMenu.setText("Share My Sheet!");
-        shareMySheetMenu.addActionListener(this::shareMySheetMenuActionPerformed);
         editMenu.add(shareMySheetMenu);
         this.add(editMenu);
 
         viewMenu.setText("View");
         showChatWindowMenu.setText("Chat Window");
-        showChatWindowMenu.addActionListener(this::showChatWindowMenuActionPerformed);
         viewMenu.add(showChatWindowMenu);
         this.add(viewMenu);
 
@@ -72,23 +70,18 @@ public class MenuBar extends JMenuBar {
         this.add(helpMenu);
     }
 
-    private void showChatWindowMenuActionPerformed(java.awt.event.ActionEvent evt) {
+    public javax.swing.JMenuItem getShowChatWindowMenu(){
-        mainWindow.showChatWindow();
+        return this.showChatWindowMenu;
+    }
+
+    public javax.swing.JCheckBoxMenuItem getShareMySheetMenu(){
+        return this.shareMySheetMenu;
     }
 
     private void aboutMenuActionPerformed(java.awt.event.ActionEvent evt) {
         mainWindow.showAboutWindow();
     }
 
-    private void shareMySheetMenuActionPerformed(java.awt.event.ActionEvent evt) {
-        mainWindow.shareMySheet(shareMySheetMenu.isSelected());
-        if (shareMySheetMenu.isSelected()) {
-            shareMySheetMenu.setText("Stop sharing it!");
-        } else {
-            shareMySheetMenu.setText("Share My Sheer!");
-        }
-    }
-
     private void closeTabMenuActionPerformed(java.awt.event.ActionEvent evt) {
         mainWindow.closeCurrentTab();
     }

src/br/edu/ufsj/sms/Main.java

@@ -6,6 +6,8 @@
 package br.edu.ufsj.sms;
 
 import br.edu.ufsj.sms.GUI.Login;
+import br.edu.ufsj.sms.net.Socket;
+import br.edu.ufsj.sms.control.ShareMySheetCtr;
 import java.net.UnknownHostException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -43,6 +45,9 @@ public class Main {
         }
         //</editor-fold>
 
+        Socket socket = new Socket();
+        socket.run();
+
         /* Create and display the form */
         java.awt.EventQueue.invokeLater(new Runnable() {
             @Override
@@ -55,6 +60,7 @@ public class Main {
                     login.dispose();
                     br.edu.ufsj.sms.GUI.MainWindow main;
                     main = new br.edu.ufsj.sms.GUI.MainWindow(name, port);
+                    ShareMySheetCtr control = new ShareMySheetCtr(name, port, socket, main);
                     main.setVisible(true);
                 } catch (UnknownHostException ex) {
                     Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);

src/br/edu/ufsj/sms/control/AlarmClock.java

@@ -14,14 +14,14 @@ import java.util.TimerTask;
  */
 public class AlarmClock extends TimerTask {
 
-    private final MainWindow mainWindow;
+    private final ShareMySheetCtr controller;
     
-    public AlarmClock(MainWindow mainWindow) {
+    public AlarmClock(ShareMySheetCtr controller) {
-        this.mainWindow = mainWindow;
+        this.controller = controller;
     }
 
     @Override
     public void run() {
-        this.mainWindow.sendScreenCastMessage();
+        this.controller.sendScreenCastMessage();
     }
 }

src/br/edu/ufsj/sms/control/ImageTransformation.java

@@ -22,6 +22,8 @@ import javax.imageio.stream.ImageOutputStream;
  */
 public class ImageTransformation {
 
+    public static float  compressRatio = 0.5f;
+
     public static byte[] toByteArray(BufferedImage image) throws IOException {
         ByteArrayOutputStream baos = new ByteArrayOutputStream();
         ImageIO.write(image, "jpg", baos);
@@ -29,13 +31,13 @@ public class ImageTransformation {
         return data;
     }
 
-    public static byte[] compress(BufferedImage image, float scale) throws IOException {
+    public static byte[] compress(BufferedImage image) throws IOException {
         ByteArrayOutputStream baos = new ByteArrayOutputStream();
         Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("jpg");
         ImageWriter writer = writers.next();
         ImageWriteParam param = writer.getDefaultWriteParam();
         param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
-        param.setCompressionQuality(scale);
+        param.setCompressionQuality(compressRatio);
         ImageOutputStream ios = ImageIO.createImageOutputStream(baos);
         writer.setOutput(ios);
         writer.write(null, new IIOImage(image, null, null), param);

src/br/edu/ufsj/sms/control/MessageSubscriber.java

@@ -0,0 +1,9 @@
+package br.edu.ufsj.sms.control; // ou o pacote onde preferir organizar suas interfaces
+
+public interface MessageSubscriber {
+    /**
+     * Método chamado pelo Socket sempre que um novo pacote for recebido e deserializado.
+     * * @param message O objeto recebido da rede (ex: ChatMessage, ScreenCastMessage)
+     */
+    void onMessageReceived(Object message);
+}

src/br/edu/ufsj/sms/control/ShareMySheetCtr.java

@@ -0,0 +1,120 @@
+package br.edu.ufsj.sms.control;
+
+import br.edu.ufsj.sms.net.Socket;
+import br.edu.ufsj.sms.GUI.MainWindow;
+import br.edu.ufsj.sms.control.AlarmClock;
+import br.edu.ufsj.sms.control.ImageTransformation;
+import br.edu.ufsj.sms.GUI.ChatWindow;
+import br.edu.ufsj.sms.GUI.MenuBar;
+
+import java.io.IOException;
+import java.util.logging.Logger;
+import java.util.logging.Level;
+import java.awt.image.BufferedImage;
+import java.awt.AWTException;
+import java.util.Timer;
+import javax.swing.JMenuBar;
+//import java.io.IOException;
+
+public class ShareMySheetCtr implements MessageSubscriber {
+
+    private MainWindow window;
+    private Socket socket;
+    private String name;
+    private int port;
+    private Timer timer;
+    private AlarmClock alarmClock;
+    public final static int TIME = 1000;
+
+    public ShareMySheetCtr (String name, int port, Socket socket, MainWindow window){
+        this.name = name;
+        this.port = port;
+        this.socket = socket;
+        this.window = window;
+
+        ChatWindow chatWindow = window.getChatWindow();
+        MenuBar menuBar = window.getSMSMenuBar();
+
+        socket.subscribe(this);
+        
+        chatWindow.getButton().addActionListener(e -> {
+            String msg = chatWindow.getText();
+            this.sendChatMessage(msg);
+        });
+
+        chatWindow.getJTextArea().addKeyListener(new java.awt.event.KeyAdapter() {
+            @Override
+            public void keyTyped(java.awt.event.KeyEvent evt) {
+                if (evt.getKeyChar() == '\n') {
+                    String msg = chatWindow.getText();
+                    sendChatMessage(msg);
+                    evt.consume();
+                }
+            }
+        });
+
+        menuBar.getShowChatWindowMenu().addActionListener(e -> {
+            window.showChatWindow();
+        });
+
+        javax.swing.JCheckBoxMenuItem shareMySheetMenu;
+        
+        shareMySheetMenu.addActionListener(e -> {
+             shareMySheet(shareMySheetMenu.isSelected());
+             if (shareMySheetMenu.isSelected()) {
+                 shareMySheetMenu.setText("Stop sharing it!");
+             } else {
+                 shareMySheetMenu.setText("Share My Sheer!");
+             }
+        });
+    }
+
+    public void onMessageReceived(Object message){  
+        if (message instanceof ScreenCastMessage) {
+            this.window.receiveScreenCastMessage((ScreenCastMessage) message);
+        }
+        if (message instanceof ChatMessage) {
+            this.window.receiveChatMessage((ChatMessage) message);
+        }
+    }
+    
+    public void sendChatMessage(String text) {
+        ChatMessage message = new ChatMessage(this.name, text);
+        try {
+            this.socket.send(message.toByteArray());
+        } catch (IOException ex) {
+            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
+        }
+    }
+
+    public void sendScreenCastMessage() {
+        byte[] msg = null;
+        try {
+            BufferedImage image = ScreenShot.takeAShot();
+            BufferedImage rescaled = ImageTransformation.resize(image, 1024, 768);
+            byte[] byteImage = ImageTransformation.compress(rescaled);
+            ScreenCastMessage message = new ScreenCastMessage(this.name, byteImage);
+            msg = message.toByteArray();
+        } catch (AWTException | IOException ex) {
+            Logger.getLogger(AlarmClock.class.getName()).log(Level.SEVERE, null, ex);
+        }
+        if (msg != null) {
+            try {
+                this.socket.send(msg);
+            } catch (IOException ex) {
+                Logger.getLogger(AlarmClock.class.getName()).log(Level.SEVERE, null, ex);
+                ImageTransformation.compressRatio -= 0.05f;
+            }
+        }
+    }
+
+    public void shareMySheet(boolean status) {
+        if (status) {
+            this.timer = new Timer();
+            this.alarmClock = new AlarmClock(this);
+            this.timer.scheduleAtFixedRate(this.alarmClock, 0, ShareMySheetCtr.TIME);
+        } else {
+            this.timer.cancel();
+        }
+    }
+}

src/br/edu/ufsj/sms/net/Socket.java

@@ -6,6 +6,7 @@
 package br.edu.ufsj.sms.net;
 
 import br.edu.ufsj.sms.GUI.MainWindow;
+import br.edu.ufsj.sms.control.MessageSubscriber;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.ObjectInput;
@@ -16,6 +17,8 @@ import java.net.MulticastSocket;
 import java.net.UnknownHostException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import java.util.List;
+import java.util.ArrayList;
 
 /**
  *
@@ -27,9 +30,9 @@ public class Socket extends Thread {
     private InetAddress address;
     private MainWindow main;
     public final static String INET_ADDR = "224.0.0.3";
+    private final List<MessageSubscriber> subscribers = new ArrayList<>();
 
-    public Socket(MainWindow main) throws UnknownHostException {
+    public Socket() throws UnknownHostException {
-        this.main = main;
         this.address = InetAddress.getByName(Socket.INET_ADDR);
         try {
             multicastSocket = new MulticastSocket(this.main.getPort());
@@ -59,15 +62,16 @@ public class Socket extends Thread {
             ObjectInput in = new ObjectInputStream(bis);
             Object message;
             message = in.readObject();
-            if (message instanceof ScreenCastMessage) {
+            for (MessageSubscriber sub : subscribers) {
-                this.main.receiveScreenCastMessage((ScreenCastMessage) message);
+                sub.onMessageReceived(message);
-            }
-            if (message instanceof ChatMessage) {
-                this.main.receiveChatMessage((ChatMessage) message);
             }
         }
     }
 
+    public void subscribe(MessageSubscriber sub) {
+        this.subscribers.add(sub);
+    }
+
     @Override
     public void run() {
         try {