Java - Chatting Room

// Server.java
package chatRoom;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;

public class Server {

    private ServerSocket serverSocket;
    ArrayList<NewClient> clientArray = new ArrayList<NewClient>();

    int PORT = 4447;
    //int MAX = 30;

    public Server() throws IOException {

        serverSocket = new ServerSocket(PORT);
        System.out.println("Server Connected...");

        while (true) {
            Socket clientSocket = serverSocket.accept(); //accept new client
            NewClient newClient = new NewClient(this, clientSocket);
            newClient.start();

            // clientArray will be added after receiving message from client
            clientArray.add(newClient); // add client socket to ArrayList
        }
    }

    public void sendToAll(String msgFromClient) {

    }

    public static void main(String[] args) throws IOException {
        new Server();
    }
}

// NewClient.java
package chatRoom;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.StringTokenizer;

public class NewClient extends Thread {

    Socket clientSocket;
    Server server;

    BufferedReader in;
    PrintWriter out;

    String loginName = "";
    String loginIP = "";

    // LOGIN
    public NewClient(Server server, Socket clientSocket) throws IOException {

        this.server = server;
        this.clientSocket = clientSocket;

        in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        out = new PrintWriter(clientSocket.getOutputStream());

        String loginInfo = in.readLine();
        // userName@/127.0.0.1 => (userName, userIP)
        StringTokenizer tok = new StringTokenizer(loginInfo, "@");

        loginName = tok.nextToken();
        loginIP = tok.nextToken();

        sendToMe("Welcome " + loginName + loginIP);

        // ==> send the list of chatters to clients <==
        // clientArray is not added in the beginning
        // is added after run()
        // new user
        //server.clientArray.add(this);
        if (server.clientArray.size() > 0) {
            String temp = "";
            for (NewClient newClient : server.clientArray) {
                temp += (newClient.loginName + newClient.loginIP) + "@";
            }
            // send other's login info to me
            sendToMe("USERLIST@" + server.clientArray.size() + "@" + temp);
        }

        // old user
        for (NewClient newClient : server.clientArray) {
            // send my login info to other
            newClient.sendToMe("ADD@" + loginName + loginIP);
        }
    }

    // RECEIVING MESSAGE
    public void run() {
        String msgFromClient = null;
        while (true) {
            try {
                // msgFromClient = username@ALL@hello world
                msgFromClient = in.readLine();

                if (msgFromClient.equals("CLOSE")) {

                    in.close();
                    out.close();
                    clientSocket.close();

                    for (NewClient newClient : server.clientArray) {
                        newClient.sendToMe("DELETE@" + loginName);
                    }

                    server.clientArray.remove(this);

                    return;  // error without "return"

                } else {

                    // msgFromClient = username@ALL@hello world
                    StringTokenizer tok = new StringTokenizer(msgFromClient, "@");

                    String sender = tok.nextToken();
                    String receiver = tok.nextToken();
                    String content = tok.nextToken();

                    for (NewClient newClient : server.clientArray) {
                        if (receiver.equals("ALL")) {
                            if (!sender.equals(newClient.getUserName())) {
                                msgFromClient = sender + ": " + content;
                                newClient.sendToMe(msgFromClient);
                            } else {
                                msgFromClient = "Me" + ": " + content;
                                sendToMe(msgFromClient);
                            }
                        } else if (!receiver.equals("ALL")) {
                            if (newClient.getUserName().equals(receiver)) {
                                msgFromClient = sender + ": " + content;
                                newClient.sendToMe(msgFromClient);
                            }
                        }
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public void sendToMe(String msg) {
        out.println(msg);
        out.flush();
    }

    public String getUserName() {
        return loginName;
    }

    public String getUserIP() {
        return loginIP;
    }
}

// ChatGUI.java
package chatRoom;

import java.awt.event.KeyEvent;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.StringTokenizer;
import javax.swing.DefaultListModel;
import javax.swing.JOptionPane;

/**
 *
 * @author jlee
 */
public class ChatGUI extends javax.swing.JFrame {

    String hostIP = "127.0.0.1";  // server ip "localhost"
    int port = 4447;

    private Socket socket;
    private PrintWriter out;
    private BufferedReader in;

    private ReceiveMessage receiveMessage;
    private boolean isConnected = false;

    private DefaultListModel listModel;

    public ChatGUI() throws IOException {
        listModel = new DefaultListModel();
        initComponents();
    }

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

        buttonGroup = new javax.swing.ButtonGroup();
        inLogin = new javax.swing.JTextField();
        jScrollPane1 = new javax.swing.JScrollPane();
        outMessage = new javax.swing.JTextArea();
        btStart = new javax.swing.JButton();
        jScrollPane2 = new javax.swing.JScrollPane();
        userList = new javax.swing.JList(listModel);
        jPanel1 = new javax.swing.JPanel();
        btExit = new javax.swing.JButton();
        radioWisper = new javax.swing.JRadioButton();
        radioPublic = new javax.swing.JRadioButton();
        inMessage = new javax.swing.JTextField();
        btSend = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.DO_NOTHING_ON_CLOSE);

        outMessage.setEditable(false);
        outMessage.setColumns(20);
        outMessage.setRows(5);
        jScrollPane1.setViewportView(outMessage);

        btStart.setText("Start");
        btStart.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btStartActionPerformed(evt);
            }
        });

        userList.addListSelectionListener(new javax.swing.event.ListSelectionListener() {
            public void valueChanged(javax.swing.event.ListSelectionEvent evt) {
                userListValueChanged(evt);
            }
        });
        jScrollPane2.setViewportView(userList);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 0, Short.MAX_VALUE)
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGap(0, 53, Short.MAX_VALUE)
        );

        btExit.setText("Exit");
        btExit.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btExitActionPerformed(evt);
            }
        });

        buttonGroup.add(radioWisper);
        radioWisper.setText("Wisper");

        buttonGroup.add(radioPublic);
        radioPublic.setSelected(true);
        radioPublic.setText("Public");

        inMessage.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                inMessageActionPerformed(evt);
            }
        });
        inMessage.addKeyListener(new java.awt.event.KeyAdapter() {
            public void keyReleased(java.awt.event.KeyEvent evt) {
                inMessageKeyReleased(evt);
            }
        });

        btSend.setText("Send");
        btSend.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                btSendActionPerformed(evt);
            }
        });

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(inLogin, javax.swing.GroupLayout.PREFERRED_SIZE, 283, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(btStart)
                        .addGap(4, 4, 4)
                        .addComponent(btExit, javax.swing.GroupLayout.PREFERRED_SIZE, 51, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(inMessage, javax.swing.GroupLayout.PREFERRED_SIZE, 339, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(btSend))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 285, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                    .addComponent(radioWisper)
                                    .addComponent(radioPublic))
                                .addGap(0, 0, Short.MAX_VALUE))
                            .addGroup(layout.createSequentialGroup()
                                .addGap(4, 4, 4)
                                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 0, Short.MAX_VALUE)))))
                .addGap(11, 11, 11)
                .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGap(0, 0, 0))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(10, 10, 10)
                        .addComponent(inLogin, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(btExit)
                            .addComponent(btStart))))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 164, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(14, 14, 14)
                        .addComponent(radioPublic)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(radioWisper))
                    .addComponent(jScrollPane1))
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(0, 0, Short.MAX_VALUE)
                        .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(layout.createSequentialGroup()
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(inMessage, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(btSend))
                        .addContainerGap())))
        );

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

    private void inMessageActionPerformed(java.awt.event.ActionEvent evt) {
        send();
    }

    private void btSendActionPerformed(java.awt.event.ActionEvent evt) {
        send();
    }

    private void btExitActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        if (!isConnected) {
            JOptionPane.showMessageDialog(this, "Is not connected!",
                    "", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {

            // close connection to server
            boolean flag = closeConnection();

            if (flag == false) {
                throw new Exception("Close error");
            }

            JOptionPane.showMessageDialog(this, "Bye.");

        } catch (Exception exc) {
            JOptionPane.showMessageDialog(this, exc.getMessage(),
                    "", JOptionPane.ERROR_MESSAGE);
        }

    }

    private void inMessageKeyReleased(java.awt.event.KeyEvent evt) {
        // TODO add your handling code here:
//        if (evt.getKeyCode() == KeyEvent.VK_ENTER) {
//            send();
//        }
    }

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

        if (isConnected) {
            JOptionPane.showMessageDialog(this, "isConnected",
                    "", JOptionPane.ERROR_MESSAGE);
            return;
        }
        try {
            String name = inLogin.getText().trim();

            // ====> connect to server
            boolean flag = connectServer(port, hostIP, name);

            if (flag == false) {
                throw new Exception("Connection error");
            }

            this.setTitle(name);
            JOptionPane.showMessageDialog(this, "Welcome " + name);

        } catch (Exception exc) {
            JOptionPane.showMessageDialog(this, exc.getMessage(),
                    "", JOptionPane.ERROR_MESSAGE);
        }


    }

    private void userListValueChanged(javax.swing.event.ListSelectionEvent evt) {
        // TODO add your handling code here:
    }

    //LOGIN
    public boolean connectServer(int port, String hostIP, String name) {

        try {
            socket = new Socket(hostIP, port);

            out = new PrintWriter(socket.getOutputStream());
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            //LOGIN
            // name@/x.x.x.x
            sendMessage(name + "@" + socket.getLocalAddress().toString());

            //receive message
            //receiveMessage = new ReceiveMessage(in, textArea);
            receiveMessage = new ReceiveMessage();
            receiveMessage.start();

            isConnected = true;
            return true;

        } catch (Exception e) {
            outMessage.append("Server port: " + port + "Server IP: " + hostIP + "\r\n");
            isConnected = false;
            return false;
        }
    }

    @SuppressWarnings("deprecation")
    public synchronized boolean closeConnection() {
        try {

            sendMessage("CLOSE");
            receiveMessage.stop(); //NullPointerException

            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
            if (socket != null) {
                socket.close();
            }

            isConnected = false;

            System.exit(0);

            return true;

        } catch (IOException e1) {
            e1.printStackTrace();
            isConnected = true;
            return false;
        }
    }

    public void send() {
        if (!isConnected) {
            JOptionPane.showMessageDialog(this, "Is not connected!", "",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }

        String message = inMessage.getText().trim();

        if (message == null || message.equals("")) {
            JOptionPane.showMessageDialog(this, "No message", "",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }

        // username@ALL@hello world
//        sendMessage(this.getTitle() + "@" + "ALL" + "@" + message);

        if (radioWisper.isSelected()) {
            String receiver = (String) userList.getSelectedValue();

            sendMessage(this.getTitle() + "@" + receiver + "@" + message);

        } else {
            sendMessage(this.getTitle() + "@" + "ALL" + "@" + message);
        }

        inMessage.setText(null);
    }

    public void sendMessage(String message) {

        out.println(message);
        out.flush();
    }

    class ReceiveMessage extends Thread {

        public void run() {
            String msgFromServer = "";
            while (true) {
                try {

                    // => CLOSE, ADD@, DELETE@, USERLIST@, MAX@, or username: hi
                    msgFromServer = in.readLine();
                    System.out.println(msgFromServer);

                    // '/' or, '@'
                    StringTokenizer tok = new StringTokenizer(msgFromServer, "/@");

                    String command = tok.nextToken();

                    // CLOSE
                    if (command.equals("CLOSE")) {
                        outMessage.append("Server closed!\r\n");
                        removeUsers();
                        return;
                    } // MAX@username/x.x.x.x
                    //                    else if (command.equals("MAX")) {
                    //                        textArea.append("Max limited!\r\n");
                    //                        removeUsers();
                    //                        return;
                    //                    }
                    // DELETE@username
                    else if (command.equals("DELETE")) {

                        String username = tok.nextToken();

                        listModel.removeElement(username);

                        // ADD@username/x.x.x.x
                    } else if (command.equals("ADD")) {

                        String username = "";
                        String userIp = "";

                        if ((username = tok.nextToken()) != null
                                && (userIp = tok.nextToken()) != null) {

                            listModel.addElement(username);
                        }

                        // USERLIST@numOfUser@username@/x.x.x.x@username@/x.x.x.x
                    } else if (command.equals("USERLIST")) {

                        int numOfUser = Integer.parseInt(tok.nextToken());
                        String username = null;
                        String userIp = null;

                        for (int i = 0; i < numOfUser; i++) {
                            username = tok.nextToken();
                            userIp = tok.nextToken();

                            listModel.addElement(username);
                        }

                        // username: hello world
                    } else {
                        outMessage.append(msgFromServer + "\r\n");
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        public synchronized void removeUsers() throws Exception {

            listModel.removeAllElements();

            if (in != null) {
                in.close();
            }
            if (out != null) {
                out.close();
            }
            if (socket != null) {
                socket.close();
            }
            isConnected = false;
        }
    }  // end of ReceiveMessage class

    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(ChatGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(ChatGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(ChatGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(ChatGUI.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() {
                try {
                    new ChatGUI().setVisible(true);
                } catch (IOException ex) {
                }
            }
        });
    }

    // Variables declaration - do not modify
    private javax.swing.JButton btExit;
    private javax.swing.JButton btSend;
    private javax.swing.JButton btStart;
    private javax.swing.ButtonGroup buttonGroup;
    private javax.swing.JTextField inLogin;
    private javax.swing.JTextField inMessage;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JTextArea outMessage;
    private javax.swing.JRadioButton radioPublic;
    private javax.swing.JRadioButton radioWisper;
    private javax.swing.JList userList;
    // End of variables declaration
}

// Client.java
package chatRoom;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.StringTokenizer;

import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSplitPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.border.TitledBorder;

public class Client {

    private JFrame frame;
    private JList userList;
    private JTextArea textArea;
    private JTextField textField;
    private JTextField txt_port;
    private JTextField txt_hostIp;
    private JTextField txt_name;
    private JButton btn_start;
    private JButton btn_stop;
    private JButton btn_send;
    private JPanel northPanel;
    private JPanel southPanel;
    private JScrollPane rightScroll;
    private JScrollPane leftScroll;
    private JSplitPane centerSplit;

    private Socket socket;
    private PrintWriter out;
    private BufferedReader in;

    private ReceiveMessage receiveMessage;
    private boolean isConnected = false;

    private DefaultListModel listModel;

    public Client() {

        init();

        btn_start.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                int port;
                if (isConnected) {
                    JOptionPane.showMessageDialog(frame, "isConnected",
                            "", JOptionPane.ERROR_MESSAGE);
                    return;
                }
                try {
                    try {
                        port = Integer.parseInt(txt_port.getText().trim());
                    } catch (NumberFormatException e2) {
                        throw new Exception("Port error");
                    }

                    String hostIp = txt_hostIp.getText().trim();

                    String name = txt_name.getText().trim();

                    if (name.equals("") || hostIp.equals("")) {
                        throw new Exception("No Login");
                    }

                    // ====> connect to server
                    boolean flag = connectServer(port, hostIp, name);

                    if (flag == false) {
                        throw new Exception("Connection error");
                    }

                    frame.setTitle(name);
                    JOptionPane.showMessageDialog(frame, "Welcome " + name);

                } catch (Exception exc) {
                    JOptionPane.showMessageDialog(frame, exc.getMessage(),
                            "", JOptionPane.ERROR_MESSAGE);
                }
            }
        });

        btn_stop.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                if (!isConnected) {
                    JOptionPane.showMessageDialog(frame, "Is not connected!",
                            "", JOptionPane.ERROR_MESSAGE);
                    return;
                }
                try {

                    // close connection to server
                    boolean flag = closeConnection();

                    if (flag == false) {
                        throw new Exception("Close error");
                    }

                    JOptionPane.showMessageDialog(frame, "I am leaving.");

                } catch (Exception exc) {
                    JOptionPane.showMessageDialog(frame, exc.getMessage(),
                            "", JOptionPane.ERROR_MESSAGE);
                }
            }
        });

        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                if (isConnected) {

                    // close connection to server
                    closeConnection();
                }
                System.exit(0);
            }
        });

        textField.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                send();
            }
        });

        btn_send.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                send();
            }
        });

    }  // end of Client

    public void init() {

        textArea = new JTextArea();
        textArea.setEditable(false);
        textArea.setForeground(Color.blue);
        textField = new JTextField();
        txt_port = new JTextField("6666");
        txt_hostIp = new JTextField("127.0.0.1");
        txt_name = new JTextField("");
        btn_start = new JButton("Start");
        btn_stop = new JButton("Stop");
        btn_send = new JButton("Send");
        listModel = new DefaultListModel();
        userList = new JList(listModel);

        northPanel = new JPanel();
        northPanel.setLayout(new GridLayout(1, 7));
        northPanel.add(new JLabel("Port"));
        northPanel.add(txt_port);
        northPanel.add(new JLabel("IP"));
        northPanel.add(txt_hostIp);
        northPanel.add(new JLabel("Login"));
        northPanel.add(txt_name);
        northPanel.add(btn_start);
        northPanel.add(btn_stop);
        northPanel.setBorder(new TitledBorder(""));

        rightScroll = new JScrollPane(textArea);
        rightScroll.setBorder(new TitledBorder(""));
        leftScroll = new JScrollPane(userList);
        leftScroll.setBorder(new TitledBorder(""));
        southPanel = new JPanel(new BorderLayout());
        southPanel.add(textField, "Center");
        southPanel.add(btn_send, "East");
        southPanel.setBorder(new TitledBorder(""));

        centerSplit = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, leftScroll,
                rightScroll);
        centerSplit.setDividerLocation(100);

        frame = new JFrame("");
        //frame.setIconImage(Toolkit.getDefaultToolkit().createImage(Client.class.getResource("qq.png")));
        frame.setLayout(new BorderLayout());
        frame.add(northPanel, "North");
        frame.add(centerSplit, "Center");
        frame.add(southPanel, "South");
        frame.setSize(600, 400);
        int screen_width = Toolkit.getDefaultToolkit().getScreenSize().width;
        int screen_height = Toolkit.getDefaultToolkit().getScreenSize().height;
        frame.setLocation((screen_width - frame.getWidth()) / 2,
                (screen_height - frame.getHeight()) / 2);
        frame.setVisible(true);
    }

    //LOGIN
    public boolean connectServer(int port, String hostIp, String name) {

        try {
            socket = new Socket(hostIp, port);
            out = new PrintWriter(socket.getOutputStream());
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            //LOGIN
            // name@/x.x.x.x
            sendMessage(name + "@" + socket.getLocalAddress().toString());

            //receive message
            //receiveMessage = new ReceiveMessage(in, textArea);
            receiveMessage = new ReceiveMessage();
            receiveMessage.start();

            isConnected = true;
            return true;

        } catch (Exception e) {
            textArea.append("Server port: " + port + "Server IP: " + hostIp + "\r\n");
            isConnected = false;
            return false;
        }
    }

    @SuppressWarnings("deprecation")
    public synchronized boolean closeConnection() {
        try {

            sendMessage("CLOSE");
            receiveMessage.stop(); //NullPointerException

            if (in != null) { in.close(); }
            if (out != null) { out.close(); }
            if (socket != null) { socket.close(); }

            isConnected = false;
            return true;

        } catch (IOException e1) {
            e1.printStackTrace();
            isConnected = true;
            return false;
        }
    }

    public void send() {
        if (!isConnected) {
            JOptionPane.showMessageDialog(frame, "Is not connected!", "",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }

        String message = textField.getText().trim();

        if (message == null || message.equals("")) {
            JOptionPane.showMessageDialog(frame, "No message", "",
                    JOptionPane.ERROR_MESSAGE);
            return;
        }

        // username@ALL@hello world
        sendMessage(frame.getTitle() + "@" + "ALL" + "@" + message);

        textField.setText(null);
    }

    public void sendMessage(String message) {

        out.println(message);
        out.flush();
    }

    class ReceiveMessage extends Thread {

        public void run() {
            String msgFromServer = "";
            while (true) {
                try {

                    // => CLOSE, ADD@, DELETE@, USERLIST@, MAX@, or username: hi
                    msgFromServer = in.readLine();
                    System.out.println(msgFromServer);

                    // '/' or, '@'
                    StringTokenizer tok = new StringTokenizer(msgFromServer, "/@");

                    String command = tok.nextToken();

                    // CLOSE
                    if (command.equals("CLOSE")) {
                        textArea.append("Server closed!\r\n");
                        removeUsers();
                        return;
                    }
                    // MAX@username/x.x.x.x
//                    else if (command.equals("MAX")) {
//                        textArea.append("Max limited!\r\n");
//                        removeUsers();
//                        return;
//                    }
                    // DELETE@username
                    else if (command.equals("DELETE")) {

                        String username = tok.nextToken();

                        listModel.removeElement(username);

                    // ADD@username/x.x.x.x
                    } else if (command.equals("ADD")) {

                        String username = "";
                        String userIp = "";

                        if ((username = tok.nextToken()) != null
                                && (userIp = tok.nextToken()) != null) {

                            listModel.addElement(username);
                        }

                    // USERLIST@numOfUser@username@/x.x.x.x@username@/x.x.x.x
                    } else if (command.equals("USERLIST")) {

                        int numOfUser = Integer.parseInt(tok.nextToken());
                        String username = null;
                        String userIp = null;

                        for (int i = 0; i < numOfUser; i++) {
                            username = tok.nextToken();
                            userIp = tok.nextToken();

                            listModel.addElement(username);
                        }

                    // username: hello world
                    } else {
                        textArea.append(msgFromServer + "\r\n");
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        public synchronized void removeUsers() throws Exception {

            listModel.removeAllElements();

            if (in != null) { in.close(); }
            if (out != null) { out.close(); }
            if (socket != null) { socket.close(); }
            isConnected = false;
        }
    }  // end of ReceiveMessage class

    public static void main(String[] args) {
        new Client();
    }
}