java代码简单实现客户端发送信息给服务端，服务端接收信息，然后服务端发送信息回给客户端

客户端代码：

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

public class Client {
    public static void main(String[] args) {
        try {
            Socket socket = new Socket("localhost", 8888);
            // 获取输出流，向服务端发送信息
            OutputStream os = socket.getOutputStream();
            PrintWriter pw = new PrintWriter(os);
            pw.write("Hello Server!");
            pw.flush();
            socket.shutdownOutput();

            // 获取输入流，接收服务端的信息
            InputStream is = socket.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(is));
            String info;
            while ((info = br.readLine()) != null) {
                System.out.println("我是客户端，服务端说：" + info);
            }
            socket.shutdownInput();

            // 关闭资源
            br.close();
            is.close();
            pw.close();
            os.close();
            socket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

服务端代码：

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

public class Server {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket = new ServerSocket(8888);
            System.out.println("服务端已启动，等待客户端连接...");

            Socket socket = serverSocket.accept();
            // 获取输入流，接收客户端的信息
            InputStream is = socket.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(is));
            String info;
            while ((info = br.readLine()) != null) {
                System.out.println("我是服务端，客户端说：" + info);
            }
            socket.shutdownInput();

            // 获取输出流，向客户端发送信息
            OutputStream os = socket.getOutputStream();
            PrintWriter pw = new PrintWriter(os);
            pw.write("Hello Client!");
            pw.flush();
            socket.shutdownOutput();

            // 关闭资源
            pw.close();
            os.close();
            br.close();
            is.close();
            socket.close();
            serverSocket.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

这段代码实现了客户端连接到服务端后，向服务端发送信息，服务端接收到信息后再向客户端发送信息。