Java GUI - เขียน Server แบบ GUI แล้วปุ่มกดมันค้างนะครับ ใช้ netbean เขียนเอา

package network;
import java.io.*;
import java.net.*;
public class ser extends javax.swing.JFrame {
    private static Socket socket;
    public ser() {
        initComponents();
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        PORT1 = new javax.swing.JTextField();
        jLabel1 = new javax.swing.JLabel();
        IP1 = new javax.swing.JTextField();
        jLabel2 = new javax.swing.JLabel();
        jLabel5 = new javax.swing.JLabel();
        jScrollPane1 = new javax.swing.JScrollPane();
        TFLOG = new javax.swing.JTextArea();
        BTN_START = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        PORT1.setText("1234");
        PORT1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                PORT1ActionPerformed(evt);
            }
        });

        jLabel1.setFont(new java.awt.Font("Tahoma", 0, 24)); // NOI18N
        jLabel1.setText("Server");

        IP1.setText("127.0.0.1");

        jLabel2.setText("SERVER 1 : ");

        jLabel5.setText("PORT : ");

        TFLOG.setColumns(20);
        TFLOG.setRows(5);
        jScrollPane1.setViewportView(TFLOG);

        BTN_START.setText("Strat Server");
        BTN_START.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                BTN_STARTActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(47, 47, 47)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(107, 107, 107)
                        .addComponent(jLabel1))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jLabel2)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(IP1, javax.swing.GroupLayout.PREFERRED_SIZE, 88, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(jLabel5)
                                .addGap(18, 18, 18)
                                .addComponent(PORT1, javax.swing.GroupLayout.PREFERRED_SIZE, 71, javax.swing.GroupLayout.PREFERRED_SIZE))
                            .addGroup(layout.createSequentialGroup()
                                .addGap(39, 39, 39)
                                .addComponent(BTN_START))))
                    .addComponent(jScrollPane1))
                .addContainerGap(60, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jLabel1)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(IP1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel5)
                    .addComponent(PORT1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addComponent(BTN_START)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 179, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(20, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>                        

    private void PORT1ActionPerformed(java.awt.event.ActionEvent evt) {                                      
        // TODO add your handling code here:
    }                                     

    private void BTN_STARTActionPerformed(java.awt.event.ActionEvent evt) {                                          
        try
        {
 
            int port = 25000;
            ServerSocket serverSocket = new ServerSocket(port);
            TFLOG.append("Server Started and listening to the port 25000");
            System.out.println("Server Started and listening to the port 25000");
            //Server is running always. This is done using this while(true) loop
            while(true) 
            {
                //Reading the message from the client
                socket = serverSocket.accept();
                InputStream is = socket.getInputStream();
                InputStreamReader isr = new InputStreamReader(is);
                BufferedReader br = new BufferedReader(isr);
                String number = br.readLine();
                TFLOG.append("Message received from client is "+number);
 
                //Multiplying the number by 2 and forming the return message
                String returnMessage;
                try
                {
                    int numberInIntFormat = Integer.parseInt(number);
                    int returnValue = numberInIntFormat*2;
                    returnMessage = String.valueOf(returnValue) + "\n";
                }
                catch(NumberFormatException e)
                {
                    //Input was not a number. Sending proper message back to client.
                    returnMessage = "Please send a proper number\n";
                }
 
                //Sending the response back to the client.
                OutputStream os = socket.getOutputStream();
                OutputStreamWriter osw = new OutputStreamWriter(os);
                BufferedWriter bw = new BufferedWriter(osw);
                bw.write(returnMessage);
                TFLOG.append("Message sent to the client is "+returnMessage);
                bw.flush();
            }
        }
        catch (Exception e) 
        {
            e.printStackTrace();
        }
        finally
        {
            try
            {
                socket.close();
            }
            catch(Exception e){}
        }
    }                                         

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(ser.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(ser.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(ser.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(ser.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new ser().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JButton BTN_START;
    private javax.swing.JTextField IP1;
    private javax.swing.JTextField PORT1;
    private javax.swing.JTextArea TFLOG;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JScrollPane jScrollPane1;
    // End of variables declaration                   
}