Added some comments and some stability fixes

src/com/coder/client/ClientWindow.java

@@ -66,7 +66,7 @@ public class ClientWindow extends JFrame implements TreeSelectionListener {
 		leftHorizontalSpitPane.setResizeWeight(0.0);
 		this.add(leftHorizontalSpitPane);
 		
-		//show this window
+		//pack the window
 		this.pack();
 	}
 

src/com/coder/client/CoderClient.java

@@ -3,6 +3,8 @@ package com.coder.client;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
+import javax.swing.JOptionPane;
+
 import com.coder.client.LoginDialog.LoginDialogAction;
 import com.coder.server.CoderServer;
 
@@ -15,6 +17,7 @@ public class CoderClient extends Thread{
 	private int port;
 	private Session session;
 	private ClientWindow window;
+	private LoginDialog loginDialog;
 	
 	public CoderClient(String url, int port) {
 		this.url = url;
@@ -22,48 +25,72 @@ public class CoderClient extends Thread{
 		
 		this.window = new ClientWindow("CoderClient");
 		
+		
 		super.start();
 	}
 	
 	public void run(){
+		//save the previously typed user name
 		String username = "";
 		while(true){
+			//close previou session if applicable
+			closeCurrentSession();
+			
+			//setup a new session
 			this.session = Session.setupConnection(url, port);
 			if(session == null){
 				logger.info("Could not setup a connection to " + url + ":" + port);
 				continue;
 			}
 			
+			//ask for username and passwor din a dialog window
 			LoginDialog loginDialog = new LoginDialog(username, null);
-			loginDialog.setVisible(true);
+			loginDialog.setVisible(true);	//blocking
+			loginDialog.dispose();
 			if(loginDialog.getAction() == LoginDialogAction.CANCEL){
 				logger.info("Login dialog closed or canceled by the user. terminating.");
 				break;
 			}
+			
+			//authenticate the user
 			username = loginDialog.getUsername();
-			String password = loginDialog.getPassword();
+			String password = new String(loginDialog.getPassword());
 			boolean authenticated = session.authenticate(username, password);
 			if(!authenticated){
+				JOptionPane.showMessageDialog(null, "Wrong username or password", "Authentication Failed", JOptionPane.INFORMATION_MESSAGE);
 				System.out.println("Authentication failed");
 				continue;
 			}
 			
+			//start receiving traffic from the server
 			session.start();
 			
+			//show the user the main GUI
 			this.window.setVisible(true);
 			try {Thread.sleep(1000);} catch (InterruptedException e) {}
 			
+			//wait here until the session is closed for some reason
 			while(session.isConnected()){
 				Thread.yield();
 			}
 			
+			//hide the main GUI
 			logger.info("The socket was closed. terminating.");
 			this.window.setVisible(false);
 			Thread.yield();
 		}
+		closeCurrentSession();
+		this.window.dispose();
 		System.exit(0);
 	}
 	
+	private void closeCurrentSession(){
+		if(this.session != null){
+			session.close();
+			session = null;
+		}
+	}
+	
 	public static void main(String[] args){
 		int port = CoderServer.SERVER_PORT;
 		new CoderClient("127.0.0.1", port);

src/com/coder/client/LoginDialog.java

@@ -99,6 +99,8 @@ public class LoginDialog extends JDialog {
 			public void keyPressed(KeyEvent e) {
 				if(e.getKeyCode() == KeyEvent.VK_ENTER){
 					btnLogin.doClick();
+				}else if(e.getKeyCode() == KeyEvent.VK_ESCAPE){
+					btnCancel.doClick();
 				}
 			}
 
@@ -119,6 +121,8 @@ public class LoginDialog extends JDialog {
 			public void keyPressed(KeyEvent e) {
 				if(e.getKeyCode() == KeyEvent.VK_ENTER){
 					btnLogin.doClick();
+				}else if(e.getKeyCode() == KeyEvent.VK_ESCAPE){
+					btnCancel.doClick();
 				}
 			}
 
@@ -134,18 +138,24 @@ public class LoginDialog extends JDialog {
 			
         });
         
-        
+        //pack the dialog
         pack();
+        
+        //move focus to the password field if already a username has been defined. must be done after pack()
+        if(username.isEmpty() == false){
+        	pfPassword.requestFocusInWindow();
+        }
+        
         setResizable(false);
-        setLocationRelativeTo(parent);
+        setLocationRelativeTo(parent);        
     }
  
     public String getUsername() {
         return tfUsername.getText().trim();
     }
  
-    public String getPassword() {
-        return new String(pfPassword.getPassword());
+    public char[] getPassword() {
+        return pfPassword.getPassword();
     }
  
     public LoginDialogAction getAction() {

src/com/coder/client/Session.java

@@ -58,7 +58,7 @@ public class Session extends Thread {
 		return session;
 	}
 
-	private void close(){
+	public void close(){
 		if(socket != null){
 			try {
 				socket.close();
@@ -81,18 +81,20 @@ public class Session extends Thread {
 			try {
 				msg = in.readGenericObject();
 			} catch (IOException e) {
-				close();
-				return;
+				logger.log(Level.INFO, "socket is probably closed by the peer", e);
+				break;
 			}
 			if(msg == null){
-				close();
-				return;
-			}
-			if(msg != null){
+				logger.info("socket is probably closed by the peer");
+				break;
+			}else{
 				handleMessage(msg);
 			}
 			Thread.yield();
 		}
+		logger.info("the current session will be closed");
+		close();
+		return;
 	}
 	
 	public void send(CoderMessage msg) throws IOException{