java 这是一个关于使用套接字连接编写网络程序的示例。客户输入三角形的三边并发送给服务器，服务器计算三角形的面积并返回给客户。

好的，以下是使用 Java 编写的简单客户端-服务器网络程序示例：

服务器端代码：

import java.io.*;
import java.net.*;
import java.util.Scanner;

public class Server {
    public static void main(String[] args) {
        try {
            // 创建服务器套接字并监听客户端请求
            ServerSocket serverSocket = new ServerSocket(8000);
            System.out.println("Server is listening...");

            while (true) {
                // 接受客户端连接
                Socket clientSocket = serverSocket.accept();
                System.out.println("Connection from: " + clientSocket.getInetAddress());

                try {
                    // 读取客户端发送的三角形三边
                    BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                    String[] sides = in.readLine().split(" ");
                    double a = Double.parseDouble(sides[0]);
                    double b = Double.parseDouble(sides[1]);
                    double c = Double.parseDouble(sides[2]);
                    System.out.println("Received: " + a + " " + b + " " + c);

                    // 计算三角形面积并发送给客户端
                    double p = (a + b + c) / 2;
                    double area = Math.sqrt(p * (p - a) * (p - b) * (p - c));
                    PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
                    out.println(area);
                    System.out.println("Sent: " + area);
                } catch (Exception e) {
                    e.printStackTrace();
                }

                // 关闭客户端连接
                clientSocket.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

客户端代码：

import java.io.*;
import java.net.*;
import java.util.Scanner;

public class Client {
    public static void main(String[] args) {
        try {
            // 创建客户端套接字并连接服务器
            Socket clientSocket = new Socket("localhost", 8000);

            while (true) {
                // 输入三角形三边并发送给服务器
                Scanner scanner = new Scanner(System.in);
                System.out.print("Enter three sides of triangle: ");
                double a = scanner.nextDouble();
                double b = scanner.nextDouble();
                double c = scanner.nextDouble();
                PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
                out.println(a + " " + b + " " + c);

                // 接受服务器返回的三角形面积并输出
                BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                double area = Double.parseDouble(in.readLine());
                System.out.println("Area: " + area);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

当客户端运行时，它将要求用户输入三角形的三边，并将其发送到服务器。服务器接收这些数据，计算三角形面积并将其发送回客户端。客户端接收并显示面积。