import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class TCPServer {

    public static void main(String[] args) {
        ServerSocket serverSocket = null;

        try {
            // 创建服务器端的Socket，监听指定端口
            serverSocket = new ServerSocket(12345);
            System.out.println("Server is listening on port 12345...");

            while (true) {
                // 等待客户端连接
                Socket clientSocket = serverSocket.accept();
                System.out.println("Client connected: " + clientSocket.getInetAddress());

                // 处理客户端连接
                handleClient(clientSocket);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (serverSocket != null && !serverSocket.isClosed()) {
                    serverSocket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private static void handleClient(Socket clientSocket) {
        try {
            // 获取输入流和输出流
            InputStream inputStream = clientSocket.getInputStream();
            OutputStream outputStream = clientSocket.getOutputStream();

            // 读取客户端发送的数据
            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                String receivedData = new String(buffer, 0, bytesRead);
                System.out.println("Received from client: " + receivedData);

                // 发送响应给客户端
                String responseData = "Hello, Client!";
                outputStream.write(responseData.getBytes());
                outputStream.flush();
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                // 关闭与客户端的连接
                clientSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;

public class TCPClient {

    public static void main(String[] args) {
        Socket socket = null;

        try {
            // 创建客户端的Socket，连接服务器端
            socket = new Socket("localhost", 12345);
            System.out.println("Connected to server...");

            // 获取输入流和输出流
            InputStream inputStream = socket.getInputStream();
            OutputStream outputStream = socket.getOutputStream();

            // 发送数据给服务器
            String requestData = "Hello, Server!";
            outputStream.write(requestData.getBytes());
            outputStream.flush();

            // 读取服务器的响应
            byte[] buffer = new byte[1024];
            int bytesRead = inputStream.read(buffer);
            String responseData = new String(buffer, 0, bytesRead);
            System.out.println("Received from server: " + responseData);

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                // 关闭与服务器的连接
                if (socket != null && !socket.isClosed()) {
                    socket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}