采用套接字技术，设计多线程程序使之能同时与多个客户通讯。 （一）三人聊天（采用TCP、UDP或者广播方式之一） 实现三个人聊天：一个人在自己客户端窗口输入“hello”，回车后另外两个人的客户端窗口都显示“hello”；三个人彼此聊天；三个人可以在不同机器上进行聊天。Java代码实现

很高兴回答你的问题！以下是一个基于Java的多线程聊天程序的实现，采用TCP协议：

服务端代码：

import java.io.*;
import java.net.*;

public class ChatServer {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(8888);
            System.out.println("服务器已启动，等待客户端的连接...");

            while (true) {
                Socket socket = serverSocket.accept();
                System.out.println("客户端" + socket.getInetAddress() + "已连接");

                new Thread(new ServerThread(socket)).start();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class ServerThread implements Runnable {
    private Socket socket;

    public ServerThread(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            BufferedWriter writer;

            while (true) {
                String message = reader.readLine();
                if (message == null) {
                    break;
                }

                System.out.println("客户端" + socket.getInetAddress() + "说：" + message);

                // 将消息发送给所有连接的客户端
                for (Socket client : ChatServerManager.clients) {
                    if (client != null && client != socket) {
                        writer = new BufferedWriter(new OutputStreamWriter(client.getOutputStream()));
                        writer.write(message + "\n");
                        writer.flush();
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

class ChatServerManager {
    public static Socket[] clients = new Socket[3];
}

客户端代码：

import java.io.*;
import java.net.*;

public class ChatClient {
    public static void main(String[] args) {
        try {
            Socket socket = new Socket("localhost", 8888);
            System.out.println("已连接到服务器");

            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
            BufferedReader serverReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));

            // 将自己的socket对象存储到ChatServerManager中，以便在服务端转发消息时使用
            for (int i = 0; i < ChatServerManager.clients.length; i++) {
                if (ChatServerManager.clients[i] == null) {
                    ChatServerManager.clients[i] = socket;
                    break;
                }
            }

            new Thread(new ClientThread(serverReader)).start();

            while (true) {
                String message = reader.readLine();
                writer.write(message + "\n");
                writer.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class ClientThread implements Runnable {
    private BufferedReader reader;

    public ClientThread(BufferedReader reader) {
        this.reader = reader;
    }

    @Override
    public void run() {
        try {
            while (true) {
                String message = reader.readLine();
                if (message == null) {
                    break;
                }

                System.out.println("收到消息：" + message);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class ChatServerManager {
    public static Socket[] clients = new Socket[3];
}

以上是一个简单的实现，可以在本地或不同机器上的三个客户端之间进行聊天。需要注意的是，如果要在不同机器上进行聊天，需将服务端代码部署到公网服务器上，且客户端需要知道服务器的公网IP地址。