Java:如何启动客户端或服务器，取决于服务器是否已经启动？

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

public class Server {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(12345); // 监听端口号为12345
            System.out.println("服务器已启动，等待客户端连接...");

            Socket clientSocket = serverSocket.accept(); // 等待客户端连接
            System.out.println("客户端已连接");

            // 获取输入输出流
            BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
            PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);

            // 接收客户端消息
            String message = in.readLine();
            System.out.println("客户端消息: " + message);

            // 向客户端发送消息
            out.println("已收到您的消息");

            // 关闭连接
            in.close();
            out.close();
            clientSocket.close();
            serverSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

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

public class Client {
    public static void main(String[] args) {
        try {
            Socket socket = new Socket("服务器IP地址", 12345); // 连接服务器IP地址和端口号
            System.out.println("已连接服务器");

            // 获取输入输出流
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

            // 向服务器发送消息
            out.println("Hello, Server");

            // 接收服务器消息
            String message = in.readLine();
            System.out.println("服务器消息: " + message);

            // 关闭连接
            in.close();
            out.close();
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}