多个客户端使用Socket通过一个服务器进行交互的小例子

import java.awt.BorderLayout;
import java.awt.Frame;
import java.awt.TextArea;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.net.Socket;
import java.net.SocketException;
import java.net.UnknownHostException;

public class ChatClient extends Frame {
    private static final long serialVersionUID = 1L;
    private Socket socket;// 声明socket对象
    private TextArea textArea = new TextArea();// 实例化文本域
    private TextField textField = new TextField();// 实例化文本框
    private DataOutputStream dos;// 输出字节流
    private DataInputStream dis;// 输入字节流
    private boolean isConnected;// 标记位，代表是否已经连接上
    Thread thread = new Thread(new RecvThread());// 实例化接收其他客户端发送的消息线程

    public static void main(String[] args) {
        new ChatClient().launchFrame();
    }

    public void launchFrame() {
        setLocation(400, 300);// 设置位置
        setSize(500, 500);// 设置大小
        add(textArea, BorderLayout.NORTH);
        add(textField, BorderLayout.SOUTH);
        pack();// 组件自适应窗口
        addWindowListener(new WindowAdapter() {// 添加窗口监听器，使用匿名类的方式实现
            @Override
            public void windowClosing(WindowEvent e) {
                disConnect();// 关闭连接
                System.exit(0);// 退出
            }
        });
        textField.addActionListener(new TFListener());// 为文本框注册监听事件
        setVisible(true);
        connect();
        thread.start();// 启动线程
    }

    public void connect() {
        try {
            socket = new Socket("127.0.0.1", 64444);
            dos = new DataOutputStream(socket.getOutputStream());
            dis = new DataInputStream(socket.getInputStream());
            isConnected = socket.isConnected();
            System.out.print("LocalAddress->" + socket.getLocalAddress() + ",LocalPort" + socket.getLocalPort());
            System.out.println("succeed connected!");
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // TextField的监听器类
    private class TFListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            String content = textField.getText().trim();
            String text = textArea.getText();
            if (!"".equals(text))
                text += "\n";
            text += content;// 将内容重新拼接，主要是取出之前的内容，添加textField中的内容，然后重新显示
            textArea.setText(text);
            textField.setText("");// 将textField文本框置空
            try {
                dos.writeUTF(content);// 向服务器端输出信息
                dos.flush();// 刷新缓冲区
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
    }

    public void disConnect() {
        try {
            if (dos != null)
                dos.close();
            if (socket != null)
                socket.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println(e.getMessage());
        }
    }

    private class RecvThread implements Runnable {
        public void run() {
            try {
                while (isConnected) {
                    String str = dis.readUTF();
                    textArea.setText(textArea.getText() + str + "\n");
                }
            } catch (SocketException e) {
                System.out.println("Good bye!" + e.getMessage());
            } catch (EOFException e) {
                System.out.println("Good bye - bye!" + e.getMessage());
            } catch (IOException e) {
                e.printStackTrace();
                System.out.println(e.getMessage());
            }

        }

    }
}

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketAddress;
import java.util.ArrayList;
import java.util.List;

public class ChatServer {
    static ServerSocket serverSocket;
    boolean isStarted = false;// 标志是否启动
    List<Client> clients = new ArrayList<ChatServer.Client>();

    public static void main(String[] args) {
        new ChatServer().start();
    }

    public void start() {
        try {
            serverSocket = new ServerSocket(64444);// 在固定的端口上进行监听
            isStarted = true;
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            while (isStarted) {
                Socket s = serverSocket.accept();// 接受连接请求
                SocketAddress remoteSocketAddress = s.getRemoteSocketAddress();
                System.out.println(remoteSocketAddress.toString());
                System.out.println("a client connected!");
                Client c = new Client(s);// 启动一个线程
                new Thread(c).start();
                clients.add(c);// 加入客户端集合，以便将消息群发给每一个客户端
            }
        } catch (Exception e) {
            System.out.println(e.getMessage());
        } finally {
            try {
                if (serverSocket != null)
                    serverSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    class Client implements Runnable {
        private Socket socket;
        private boolean connected = false;
        private DataInputStream dataInputStream;
        private DataOutputStream dataOutputStream;

        public Client(Socket s) {
            this.socket = s;
            try {
                dataInputStream = new DataInputStream(socket.getInputStream());
                dataOutputStream = new DataOutputStream(socket.getOutputStream());
                connected = socket.isConnected();
                System.out.println("connected = " + connected);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void run() {
            String content = null;
            try {
                Client client = null;
                while (connected) {
                    try {
                        content = dataInputStream.readUTF();
                        System.out.println(content);
                        System.out.println("clients.size()=>" + clients.size());
                        for (int i = 0; i < clients.size(); i++) {
                            client = clients.get(i);
                            // 分别向每一个客户端发消息
                            if (client != this)
                                client.dataOutputStream.writeUTF(content);
                        }
                    } catch (EOFException e) {
                        clients.remove(client);// 将客户端移出集合
                        System.out.println(e.getMessage());
                        System.out.println("Client closed!");
                    }
                }
            } catch (Exception e) {
                System.out.println(e.getMessage());
            } finally {
                try {
                    if (dataInputStream != null)
                        dataInputStream.close();
                    if (dataOutputStream != null) {
                        dataOutputStream.close();
                    }
                    if (socket != null)
                        socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        }
    }
}