Java请使用Socket类、ServerSocket类等编写一个套接字程序。服务器端提供报时服务：当客户端发送出“几点了？”，服务器端向客户端返回“15:40”；若客户端发送“今天是几号？”，服务器端向客户端返回“5月22日”；若客户端发送“今天是星期几？”，服务器端向客户端返回“星期一”；客户端收到数据后将在命令行窗口中显示收到的时间信息；当客户端发送“再见”时，则服务器端结束对该客户端的服务；服务器端可以同时与多个客户端建立连接，并为它们提供报时服务。

以下是一个简单的Java套接字程序，实现了服务器端提供报时服务，同时支持多个客户端连接：

服务器端代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class TimeServer {
    private static final int PORT = 8888; // 服务器端口号

    public static void main(String[] args) {
        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(PORT);
            System.out.println("服务器已启动，等待客户端连接...");
            while (true) {
                Socket clientSocket = serverSocket.accept(); // 等待客户端连接
                System.out.println("客户端 " + clientSocket.getInetAddress() + " 已连接");
                Thread thread = new Thread(new TimeServerHandler(clientSocket)); // 创建新线程处理客户端请求
                thread.start();
            }
        } catch (IOException e) {
            System.out.println("启动服务器失败：" + e.getMessage());
        } finally {
            if (serverSocket != null) {
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    // ignore
                }
            }
        }
    }
}

// 用于处理客户端请求的线程类
class TimeServerHandler implements Runnable {
    private Socket clientSocket;
    private BufferedReader in;
    private PrintWriter out;

    public TimeServerHandler(Socket socket) {
        this.clientSocket = socket;
    }

    public void run() {
        try {
            in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            out = new PrintWriter(clientSocket.getOutputStream(), true);
            String request;

            while ((request = in.readLine()) != null) {
                if ("几点了？".equals(request)) {
                    // 返回当前时间
                    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm");
                    String response = sdf.format(new Date());
                    out.println(response);
                } else if ("今天是几号？".equals(request)) {
                    // 返回当前日期
                    SimpleDateFormat sdf = new SimpleDateFormat("MM月dd日");
                    String response = sdf.format(new Date());
                    out.println(response);
                } else if ("今天是星期几？".equals(request)) {
                    // 返回当前星期几
                    Calendar calendar = Calendar.getInstance();
                    int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);
                    String[] weekDays = {"", "星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"};
                    String response = weekDays[dayOfWeek];
                    out.println(response);
                } else if ("再见".equals(request)) {
                    // 结束服务
                    System.out.println("客户端 " + clientSocket.getInetAddress() + " 已断开连接");
                    break;
                } else {
                    // 未知请求
                    out.println("无法识别的请求");
                }
            }
        } catch (IOException e) {
            System.out.println("客户端 " + clientSocket.getInetAddress() + " 连接发生异常：" + e.getMessage());
        } finally {
            try {
                if (in != null) in.close();
                if (out != null) out.close();
                clientSocket.close();
            } catch (IOException e) {
                // ignore
            }
        }
    }
}

客户端代码：

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

public class TimeClient {
    private static final String HOST = "localhost"; // 服务器地址
    private static final int PORT = 8888; // 服务器端口号

    public static void main(String[] args) {
        Socket socket = null;
        BufferedReader in = null;
        PrintWriter out = null;
        try {
            socket = new Socket(HOST, PORT);
            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            out = new PrintWriter(socket.getOutputStream(), true);

            // 发送请求
            out.println("几点了？");
            System.out.println(in.readLine());
            out.println("今天是几号？");
            System.out.println(in.readLine());
            out.println("今天是星期几？");
            System.out.println(in.readLine());
            out.println("再见");

        } catch (IOException e) {
            System.out.println("连接服务器失败：" + e.getMessage());
        } finally {
            try {
                if (in != null) in.close();
                if (out != null) out.close();
                if (socket != null) socket.close();
            } catch (IOException e) {
                // ignore
            }
        }
    }
}

运行该程序，先启动服务器端，再启动多个客户端，可以看到每个客户端都可以与服务器端建立连接，并获取当前时间、日期、星期几的信息。当客户端发送“再见”时，服务器端会结束对该客户端的服务。