环境：Notpad ++ 6.0 + JDK 6.0.31
问题：使用套接字编写客户—服务器程序，实现客户—服务器交互计算。客户将三角形3个边的长度发给服务器，服务器把计算出的三角形的面积返回给客户。
解决：利用Java的Socket编程。客户端发送数据，服务端接收数据，并进行相应的处理。
代码：
TcpServer.java：
import java.io.BufferedReader;import java.io.InputStreamReader;import java.net.ServerSocket;import java.net.Socket;public class TcpServer {public static final int NUM = 3;public static void main(String args[]){TcpServer tcpServer = new TcpServer();try {ServerSocket server = null;try {server = new ServerSocket(4700);} catch (Exception e) {e.printStackTrace();}Socket socket = null;try {socket = server.accept();} catch (Exception e) {e.printStackTrace();}String line = "";double a[] = new double[NUM];BufferedReader is = new BufferedReader(new InputStreamReader(socket.getInputStream()));System.out.println("从客户端接收三角形的三条边：");for (int i = 0; i < a.length; i++) {line = is.readLine();a[i] = Double.parseDouble(line);}System.out.println("三角形的面积是：" + tcpServer.countarea(a));is.close();//关闭读取流socket.close();//关闭Socketserver.close();//关闭ServerSocket} catch (Exception e) {e.printStackTrace();}}//计算三角形面积的方法public double countarea(double a[]){double area = 0.0;double temp = 0.0;double aside = 0.0;double bside = 0.0;double cside = 0.0;aside = a[0];bside = a[1];cside = a[2];temp = a[0] + a[1] + a[2];temp = temp / 2;area = Math.sqrt(temp * (temp - aside) * (temp - bside) * (temp - cside));return area;}}
TcpClient.java
import java.io.BufferedReader;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.Socket;public class TcpClient {public static final int NUM = 3;public static void main(String args[]){try {Socket socket = new Socket("127.0.0.1", 4700);BufferedReader sin = new BufferedReader(new InputStreamReader(System.in));PrintWriter os = new PrintWriter(socket.getOutputStream());System.out.println("从客户端接收三角形的三条边发送到服务器：");System.out.println("请输入3条边：");String readline = "";for (int i = 0; i < NUM; i++) {os.flush();readline = sin.readLine();os.println(readline);}os.close();socket.close();} catch (Exception e) {e.printStackTrace();}}}
运行：
把客户端程序（TcpClient.java）和服务端程序（TcpServer.java）分别编译，再打开两个Cmd控制台，先运行服务端，再运行客户端，在客户端输入数据，然后就可以在服务端看到结果。
运行效果截图：
服务端：
客户端：
木已成舟便要顺其自然
