My GUI freezes

Question

Hey, I'm writing a small client/server application and I'm getting a problem, when I start the server the GUI freezes and I haven't been able to solve the problem. Any help will be much appreciated.
I use 2 classes, Server which handles the serversocket and its connections, and serverInterface which handles the server's GUI.
Here is the code for the server class:
public class Server extends JFrame {
     private serverInterface interfaz=null;
     public int fileCant = 0;
     static boolean listening = true;
     private String[][] listFiles = null;
     private int ifiles=0;
     public Server(){
          this.interfaz = new serverInterface(this);          
     public void buttonPressed (int button){
          switch(button){
            case 0: {  try{startServer();}
                       catch(IOException e){System.err.println("Could not listen on port: 7777.");}
                       break;
                     } //se presiono el boton de start
            case 1: {stopServer(); break;} // se presiono el boton de stop
     private void startServer() throws IOException{
          ServerSocket serverSocket = null;
          listFiles = new String[1000][4];
        try {
             updateVal(1,"0","0",0);
            serverSocket = new ServerSocket(7777);           
        } catch (IOException e) {
            System.err.println("Could not listen on port: 7777.");
            //System.exit(1);
        while(listening){
             new multiServer(serverSocket.accept(),this).start();
     private void stopServer(){          
          System.exit(-1);
     private void updateVal(int variableUpdate,String ip, String port, int numFiles){
          this.interfaz.updateVal(variableUpdate,ip,port,numFiles);          
     public static void main(String[] args){
               new Server();
     public void addFiles(Object object, String IP, String Port){
          Vector test = (Vector) object;
          for (int i=0;i<test.size();i++){
               listFiles[ifiles][0]=(String)test.elementAt(i);
               listFiles[ifiles][1]= IP;
               listFiles[ifiles][2]=Port;
               listFiles[ifiles][3]="online";
               ifiles++;               
     public void removeFiles(String IP, String Port){
          for (int i =0;i<ifiles;i++){
               if((IP.equals(listFiles[1]))&&(Port.equals(listFiles[i][2]))){
                    listFiles[i][3] = "offline";
     public DefaultTableModel searchFile(String file){
          DefaultTableModel model = new DefaultTableModel();
          model.addColumn("File");
          model.addColumn("IP Address");
          model.addColumn("Port");
          model.addColumn(" ruta");
          for (int i=0;i<ifiles;i++){               
               if((listFiles[i][0].contains(file))&&(listFiles[i][3].equals("online"))){
                    String a[]={file,listFiles[i][1],listFiles[i][2],listFiles[i][0]};
                    model.addRow(a);
          return model;          

Answer 1

And here is the code for the server's Interface:
public class serverInterface extends JFrame {
     private static final long serialVersionUID = 1L;
     private JPanel jContentPane = null;
     private JPanel panelSouth = null;
     private JButton buttonStart = null;
     private JButton buttonStop = null;
     private Server servidor = null;
     private JPanel panelNorth = null;
     private JLabel labelConnect = null;
     private JPanel panelCentro = null;
     private JScrollPane scrollPanelClients = null;
     private JPanel panelOnlineClients = null;
     private JLabel labelOnlineClients = null;
     private JScrollPane scrollPanelClients1 = null;
     private JTable tablaClients = null;
     private DefaultTableModel model = new DefaultTableModel();
     public serverInterface(Server servidor) {
          super();
          this.servidor= servidor;          
          initialize();
     public void initialize() {
          servidor.setSize(545, 309);
          servidor.setContentPane(getJContentPane());
          servidor.setTitle("Server");
          servidor.setResizable(false);
          /*this.setSize(545, 309);
          this.setContentPane(getJContentPane());
          this.setTitle("Server");*/
     private JPanel getJContentPane() {
          if (jContentPane == null) {
               jContentPane = new JPanel();
               jContentPane.setLayout(new BorderLayout());
               jContentPane.add(getPanelSouth(), BorderLayout.SOUTH);
               jContentPane.add(getPanelNorth(), BorderLayout.NORTH);
               jContentPane.add(getPanelCentro(), BorderLayout.CENTER);
          return jContentPane;
     private JPanel getPanelSouth() {
          if (panelSouth == null) {
               panelSouth = new JPanel();
               panelSouth.setLayout(new FlowLayout());
               panelSouth.add(getButtonStart(), null);
               panelSouth.add(getButtonStop(), null);
          return panelSouth;
     private JButton getButtonStart() {
          if (buttonStart == null) {
               buttonStart = new JButton();
               buttonStart.setText("Start");
               buttonStart.addActionListener(new java.awt.event.ActionListener() {
                 public void actionPerformed(java.awt.event.ActionEvent evt0) {
                     servidor.buttonPressed(0);
          return buttonStart;
     private JButton getButtonStop() {
          if (buttonStop == null) {
               buttonStop = new JButton();
               buttonStop.setText("Stop");
               buttonStop.addActionListener(new java.awt.event.ActionListener() {
                 public void actionPerformed(java.awt.event.ActionEvent evt1) {
                     servidor.buttonPressed(1);
          return buttonStop;
     public void updateVal(int updatedValue,String ip, String port, int numFiles){
          switch(updatedValue){
             case 1:{  JOptionPane.showMessageDialog(this, "The Server Is Now Online");  //se conecta el server
                        labelConnect.setText("Server Online. Listening on port 7777");
                        buttonStart.setEnabled(false);
                     break;
             case 2:{ String a[] = {ip,port,numFiles+""};
                       model.addRow(a);                      
                        break;
     private JPanel getPanelNorth() {
          if (panelNorth == null) {
               GridBagConstraints gridBagConstraints = new GridBagConstraints();
               gridBagConstraints.gridx = 0;
               gridBagConstraints.gridy = 0;
               labelConnect = new JLabel();
               labelConnect.setText("Server Offline");
               panelNorth = new JPanel();
               panelNorth.setLayout(new GridBagLayout());
               panelNorth.add(labelConnect, gridBagConstraints);
          return panelNorth;
     private JPanel getPanelCentro() {
          if (panelCentro == null) {
               panelCentro = new JPanel();
               panelCentro.setLayout(new BorderLayout());
               panelCentro.add(getPanelOnlineClients(), BorderLayout.NORTH);
               panelCentro.add(getScrollPanelClients1(), BorderLayout.CENTER);
          return panelCentro;
     private JPanel getPanelOnlineClients() {
          if (panelOnlineClients == null) {
               GridBagConstraints gridBagConstraints1 = new GridBagConstraints();
               gridBagConstraints1.gridx = 0;
               gridBagConstraints1.gridy = 0;
               labelOnlineClients = new JLabel();
               labelOnlineClients.setText("Connected Clients:");
               panelOnlineClients = new JPanel();
               panelOnlineClients.setLayout(new GridBagLayout());
               panelOnlineClients.add(labelOnlineClients, gridBagConstraints1);
          return panelOnlineClients;
     private JScrollPane getScrollPanelClients1() {
          if (scrollPanelClients1 == null) {
               scrollPanelClients1 = new JScrollPane();
               scrollPanelClients1.setViewportView(getTablaClients());
          return scrollPanelClients1;
     private JTable getTablaClients() {
          if (tablaClients == null) {
               tablaClients = new JTable(model);
               model.addColumn("IP Address");
               model.addColumn("Port");
               model.addColumn("Files Shared");
               tablaClients.setEnabled(false);
          return tablaClients;
}