Selector Selector=Selector.open()；

channel.configureBlocking(false);
SelectionKey key= channel.register(selector,SelectionKey,OP_READ);

SelectionKey.OP_CONNECT
SelectionKey.OP_ACCEPT
SelectionKey.OP_READ
SelectionKey.OP_WRITE

int interestSet=SelectionKey.OP_READ|SelectionKey.OP_WRITE;

int interestSet=selectionKey.interestOps();
boolean isInterestedInAccept = (interestSet & SelectionKey.OP_ACCEPT) == SelectionKey.OP_ACCEPT；

//int readSet=selectionKey.readOps();
selectionKey.isAcceptable();//等價(jià)于selectionKey.readyOps()&SelectionKey.OP_ACCEPT
selectionKey.isConnectable();
selectionKey.isReadable();
selectionKey.isWritable();

Channel channel =selectionKey.channel();
Selector selector=selectionKey.selector();

SelectionKey key=channel.register(selector,SelectionKey.OP_READ,theObject);

selectionKey.attach(theObject);//綁定

selectionKey.attachment();

selectionKey.attach(null)

Set selectedKeys=selector.selectedKeys();

Set selectedKeys = selector.selectedKeys();
Iterator keyIterator = selectedKeys.iterator();
while(keyIterator.hasNext()) {
  SelectionKey key = keyIterator.next();
  if(key.isAcceptable()) {
    // a connection was accepted by a ServerSocketChannel.
  } else if (key.isConnectable()) {
    // a connection was established with a remote server.
  } else if (key.isReadable()) {
    // a channel is ready for reading
  } else if (key.isWritable()) {
    // a channel is ready for writing
  }
  keyIterator.remove();
}

public class ChatServer implements Runnable{
  private Selector selector;
  private SelectionKey serverKey;
  private Vector<String> usernames;
  private static final int PORT = 9999;
  SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  public ChatServer(){
    usernames = new Vector<String>();
    init();
  }
  public void init(){
    try {
      selector = Selector.open();
      //創(chuàng)建serverSocketChannel
      ServerSocketChannel serverChannel = ServerSocketChannel.open();
      ServerSocket socket = serverChannel.socket();
      socket.bind(new InetSocketAddress(PORT));
      //加入到selector中
      serverChannel.configureBlocking(false);
      serverKey = serverChannel.register(selector, SelectionKey.OP_ACCEPT);
      printInfo("server starting.......");
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
  @Override
  public void run() {
    try {
      while(true){
        //獲取就緒channel
        int count = selector.select();
        if(count > 0){
          Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
          while(iterator.hasNext()){
            SelectionKey key = iterator.next();
            //若此key的通道是等待接受新的套接字連接
            if(key.isAcceptable()){
              System.out.println(key.toString() + " : 接收");
              //一定要把這個(gè)accpet狀態(tài)的服務(wù)器key去掉，否則會(huì)出錯(cuò)
              iterator.remove();
              ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
              //接受socket
              SocketChannel socket = serverChannel.accept();
              socket.configureBlocking(false);
              //將channel加入到selector中，并一開(kāi)始讀取數(shù)據(jù)
              socket.register(selector, SelectionKey.OP_READ);
            }
            //若此key的通道是有數(shù)據(jù)可讀狀態(tài)
            if(key.isValid() && key.isReadable()){
              System.out.println(key.toString() + " : 讀");
              readMsg(key);
            }
            //若此key的通道是寫數(shù)據(jù)狀態(tài)
            if(key.isValid() && key.isWritable()){
              System.out.println(key.toString() + " : 寫");
              writeMsg(key);
            }
          }
        }
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
  private void readMsg(SelectionKey key) {
    SocketChannel channel = null;
    try {
      channel = (SocketChannel) key.channel();
      //設(shè)置buffer緩沖區(qū)
      ByteBuffer buffer = ByteBuffer.allocate(1024);
      //假如客戶端關(guān)閉了通道，這里在對(duì)該通道read數(shù)據(jù)，會(huì)發(fā)生IOException，捕獲到Exception后，關(guān)閉掉該channel，取消掉該key
      int count = channel.read(buffer);
      StringBuffer buf = new StringBuffer();
      //如果讀取到了數(shù)據(jù)
      if(count > 0){
        //讓buffer翻轉(zhuǎn)，把buffer中的數(shù)據(jù)讀取出來(lái)
        buffer.flip();
        buf.append(new String(buffer.array(), 0, count));
      }
      String msg = buf.toString();
      //如果此數(shù)據(jù)是客戶端連接時(shí)發(fā)送的數(shù)據(jù)
      if(msg.indexOf("open_") != -1){
        String name = msg.substring(5);//取出名字
        printInfo(name + " --> online");
        usernames.add(name);
        Iterator<SelectionKey> iter = selector.selectedKeys().iterator();
        while(iter.hasNext()){
          SelectionKey skey = iter.next();
          //若不是服務(wù)器套接字通道的key，則將數(shù)據(jù)設(shè)置到此key中
          //并更新此key感興趣的動(dòng)作
          if(skey != serverKey){
            skey.attach(usernames);
            skey.interestOps(skey.interestOps() | SelectionKey.OP_WRITE);
          }
        }
        //如果是下線時(shí)發(fā)送的數(shù)據(jù)
      }else if(msg.indexOf("exit_") != -1){
        String username = msg.substring(5);
        usernames.remove(username);
        key.attach("close");
        //要退出的當(dāng)前channel加上close的標(biāo)示，并把興趣轉(zhuǎn)為寫，如果write中收到了close，則中斷channel的鏈接
        key.interestOps(SelectionKey.OP_WRITE);
        Iterator<SelectionKey> iter = selector.selectedKeys().iterator();
        while(iter.hasNext()){
          SelectionKey sKey = iter.next();
          sKey.attach(usernames);
          sKey.interestOps(sKey.interestOps() | SelectionKey.OP_WRITE);
        }
        //如果是聊天發(fā)送數(shù)據(jù)
      }else{
        String uname = msg.substring(0, msg.indexOf("^"));
        msg = msg.substring(msg.indexOf("^") + 1);
        printInfo("("+uname+")說(shuō)：" + msg);
        String dateTime = sdf.format(new Date());
        String smsg = uname + " " + dateTime + "\n " + msg + "\n";
        Iterator<SelectionKey> iter = selector.selectedKeys().iterator();
        while(iter.hasNext()){
          SelectionKey sKey = iter.next();
          sKey.attach(smsg);
          sKey.interestOps(sKey.interestOps() | SelectionKey.OP_WRITE);
        }
      }
      buffer.clear();
    } catch (IOException e) {
      //當(dāng)客戶端關(guān)閉channel時(shí)，服務(wù)端再往通道緩沖區(qū)中寫或讀數(shù)據(jù)，都會(huì)報(bào)IOException，解決方法是：在服務(wù)端這里捕獲掉這個(gè)異常，并且關(guān)閉掉服務(wù)端這邊的Channel通道
      key.cancel();
      try {
        channel.socket().close();
        channel.close();
      } catch (IOException e1) {
        e1.printStackTrace();
      }
    }
  }
  private void writeMsg(SelectionKey key) {
    try {
      SocketChannel channel = (SocketChannel) key.channel();
      Object attachment = key.attachment();
      //獲取key的值之后，要把key的值置空，避免影響下一次的使用
      key.attach("");
      channel.write(ByteBuffer.wrap(attachment.toString().getBytes()));
      key.interestOps(SelectionKey.OP_READ);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
  private void printInfo(String str) {
    System.out.println("[" + sdf.format(new Date()) + "] -> " + str);
  }
  public static void main(String[] args) {
    ChatServer server = new ChatServer();
    new Thread(server).start();
  }
}

public class ChatClient {
  private static final String HOST = "127.0.0.1";
  private static int PORT = 9999;
  private static SocketChannel socket;
  private static ChatClient client;
  private static byte[] lock = new byte[1];
  //單例模式管理
  private ChatClient() throws IOException{
    socket = SocketChannel.open();
    socket.connect(new InetSocketAddress(HOST, PORT));
    socket.configureBlocking(false);
  }
  public static ChatClient getIntance(){
    synchronized(lock){
      if(client == null){
        try {
          client = new ChatClient();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      return client;
    }
  }
  public void sendMsg(String msg){
    try {
      socket.write(ByteBuffer.wrap(msg.getBytes()));
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
  public String receiveMsg(){
    String msg = null;
    try {
      ByteBuffer buffer = ByteBuffer.allocate(1024);
      StringBuffer buf = new StringBuffer();
      int count = 0;
      //不一定一次就能讀滿，連續(xù)讀
      while((count = socket.read(buffer)) > 0){
        buf.append(new String(buffer.array(), 0, count));
      }
      //有數(shù)據(jù)
      if(buf.length() > 0){
        msg = buf.toString();
        if(buf.toString().equals("close")){
          //不過(guò)不sleep會(huì)導(dǎo)致ioException的發(fā)生,因?yàn)槿绻@里直接關(guān)閉掉通道，在server里，
          //該channel在read（buffer）時(shí)會(huì)發(fā)生讀取異常，通過(guò)sleep一段時(shí)間，使得服務(wù)端那邊的channel先關(guān)閉，客戶端
          //的channel后關(guān)閉，這樣就能防止read(buffer)的ioException
          //但是這是一種笨方法
          //Thread.sleep(100);
          //更好的方法是，在readBuffer中捕獲異常后，手動(dòng)進(jìn)行關(guān)閉通道
          socket.socket().close();
          socket.close();
          msg = null;
        }
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
    return msg;
  }
}

public class SetNameFrame extends JFrame {
  private static final long serialVersionUID = 1L;
  private static JTextField txtName;
  private static JButton btnOK;
  private static JLabel label;
  public SetNameFrame() {
    this.setLayout(null);
    Toolkit kit = Toolkit.getDefaultToolkit();
    int w = kit.getScreenSize().width;
    int h = kit.getScreenSize().height;
    this.setBounds(w / 2 - 230 / 2, h / 2 - 200 / 2, 230, 200);
    this.setTitle("設(shè)置名稱");
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setResizable(false);
    txtName = new JTextField(4);
    this.add(txtName);
    txtName.setBounds(10, 10, 100, 25);
    btnOK = new JButton("OK");
    this.add(btnOK);
    btnOK.setBounds(120, 10, 80, 25);
    label = new JLabel("[w:" + w + ",h:" + h + "]");
    this.add(label);
    label.setBounds(10, 40, 200, 100);
    label.setText("<html>在上面的文本框中輸入名字<br/>顯示器寬度：" + w + "<br/>顯示器高度：" + h
        + "</html>");
    btnOK.addActionListener(new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent e) {
        String uname = txtName.getText();
        ChatClient service = ChatClient.getIntance();
        ChatFrame chatFrame = new ChatFrame(service, uname);
        chatFrame.show();
        setVisible(false);
      }
    });
  }
  public static void main(String[] args) {
    SetNameFrame setNameFrame = new SetNameFrame();
    setNameFrame.setVisible(true);
  }
}

public class ChatFrame {
  private JTextArea readContext = new JTextArea(18, 30);// 顯示消息文本框
  private JTextArea writeContext = new JTextArea(6, 30);// 發(fā)送消息文本框
  private DefaultListModel modle = new DefaultListModel();// 用戶列表模型
  private JList list = new JList(modle);// 用戶列表
  private JButton btnSend = new JButton("發(fā)送");// 發(fā)送消息按鈕
  private JButton btnClose = new JButton("關(guān)閉");// 關(guān)閉聊天窗口按鈕
  private JFrame frame = new JFrame("ChatFrame");// 窗體界面
  private String uname;// 用戶姓名
  private ChatClient service;// 用于與服務(wù)器交互
  private boolean isRun = false;// 是否運(yùn)行
  public ChatFrame(ChatClient service, String uname) {
    this.isRun = true;
    this.uname = uname;
    this.service = service;
  }
  // 初始化界面控件及事件
  private void init() {
    frame.setLayout(null);
    frame.setTitle(uname + " 聊天窗口");
    frame.setSize(500, 500);
    frame.setLocation(400, 200);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setResizable(false);
    JScrollPane readScroll = new JScrollPane(readContext);
    readScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
    frame.add(readScroll);
    JScrollPane writeScroll = new JScrollPane(writeContext);
    writeScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
    frame.add(writeScroll);
    frame.add(list);
    frame.add(btnSend);
    frame.add(btnClose);
    readScroll.setBounds(10, 10, 320, 300);
    readContext.setBounds(0, 0, 320, 300);
    readContext.setEditable(false);
    readContext.setLineWrap(true);// 自動(dòng)換行
    writeScroll.setBounds(10, 315, 320, 100);
    writeContext.setBounds(0, 0, 320, 100);
    writeContext.setLineWrap(true);// 自動(dòng)換行
    list.setBounds(340, 10, 140, 445);
    btnSend.setBounds(150, 420, 80, 30);
    btnClose.setBounds(250, 420, 80, 30);
    frame.addWindowListener(new WindowAdapter() {
      @Override
      public void windowClosing(WindowEvent e) {
        isRun = false;
        service.sendMsg("exit_" + uname);
        System.exit(0);
      }
    });
    btnSend.addActionListener(new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent e) {
        String msg = writeContext.getText().trim();
        if(msg.length() > 0){
          service.sendMsg(uname + "^" + writeContext.getText());
        }
        writeContext.setText(null);
        writeContext.requestFocus();
      }
    });
    btnClose.addActionListener(new ActionListener() {
      @Override
      public void actionPerformed(ActionEvent e) {
        isRun = false;
        service.sendMsg("exit_" + uname);
        System.exit(0);
      }
    });
    list.addListSelectionListener(new ListSelectionListener() {
      @Override
      public void valueChanged(ListSelectionEvent e) {
        // JOptionPane.showMessageDialog(null,
        // list.getSelectedValue().toString());
      }
    });
    writeContext.addKeyListener(new KeyListener() {
      @Override
      public void keyTyped(KeyEvent e) {
        // TODO Auto-generated method stub
      }
      @Override
      public void keyReleased(KeyEvent e) {
        if(e.getKeyCode() == KeyEvent.VK_ENTER){
          String msg = writeContext.getText().trim();
          if(msg.length() > 0){
            service.sendMsg(uname + "^" + writeContext.getText());
          }
          writeContext.setText(null);
          writeContext.requestFocus();
        }
      }
      @Override
      public void keyPressed(KeyEvent e) {
        // TODO Auto-generated method stub
      }
    });
  }
  // 此線程類用于輪詢讀取服務(wù)器發(fā)送的消息
  private class MsgThread extends Thread {
    @Override
    public void run() {
      while (isRun) {
        String msg = service.receiveMsg();
        if (msg != null) {
          //如果存在[]，這是verctor裝的usernames的toString生成的
          if (msg.indexOf("[") != -1 && msg.lastIndexOf("]") != -1) {
            msg = msg.substring(1, msg.length() - 1);
            String[] userNames = msg.split(",");
            modle.removeAllElements();
            for (int i = 0; i < userNames.length; i++) {
              modle.addElement(userNames[i].trim());
            }
          } else {//如果是普通的消息
            String str = readContext.getText() + msg;
            readContext.setText(str);
            readContext.selectAll();
          }
        }
      }
    }
  }
  // 顯示界面
  public void show() {
    this.init();
    service.sendMsg("open_" + uname);
    MsgThread msgThread = new MsgThread();
    msgThread.start();
    this.frame.setVisible(true);
  }
}