java实现TCP客户端，服务端相互通信

在Java中实现TCP客户端和服务端通信，通常需要使用`java.net.Socket`类（用于创建连接）和`ServerSocket`类（用于监听连接）。以下是简单的步骤：

**服务端（Server）：**

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

public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket server = new ServerSocket(8080); // 监听8080端口
        System.out.println("Server is running on port 8080");

        while (true) {
            Socket clientSocket = server.accept(); // 等待客户端连接
            try (BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                 PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true)) {

                String requestLine;
                while ((requestLine = in.readLine()) != null) { // 读取客户端数据
                    System.out.println("Received: " + requestLine);
                    out.println("Echoing: " + requestLine); // 发回给客户端
                }
            } finally {
                clientSocket.close();
            }
        }
    }
}

**客户端（Client）：**

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

public class Client {
    public static void main(String[] args) throws IOException {
        String hostname = "localhost"; // 如果是远程服务器，则替换为你服务器地址
        int port = 8080;

        Socket socket = new Socket(hostname, port);
        System.out.println("Connected to server at " + hostname + ":" + port);

        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);

        String userInput;
        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        while ((userInput = stdIn.readLine()) != null) {
            out.println(userInput); // 发送数据到服务器
            System.out.println("Sent: " + userInput);
            String response = in.readLine(); // 接收服务器响应
            System.out.println("Received: " + response);
        }

        socket.close();
    }
}

以上示例是一个基础的TCP文本通信，客户端发送一行就接收一行回复。运行服务端程序，然后在客户端启动交互。