TCP通信练习3–上传文件有一个img.jpg图片文件 客户端：将本地图片文件上传到服务器。接收服务器的反馈。 服务器：接收客户端上传的图片文件，上传完毕之后给出反馈。完整代码添加注释

在进行TCP通信时，通常我们会使用`java.net.Socket`类来建立连接，并处理数据传输。这里我会给你一个基本的示例，包括客户端和服务器的代码以及必要的注释。首先，确保你了解TCP的基本概念，如套接字（socket）创建、读写操作等。

**客户端（Client.java）：**

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

public class Client {
    public static void main(String[] args) throws IOException {
        // 创建Socket对象
        Socket socket = new Socket("localhost", 8080); // 假设服务器运行在本机的8080端口

        try (BufferedInputStream in = new BufferedInputStream(socket.getInputStream());
             BufferedOutputStream out = new BufferedOutputStream(socket.getOutputStream())) {

            // 读取图片文件
            File file = new File("img.jpg"); // 图片路径
            FileInputStream fis = new FileInputStream(file);

            // 获取文件长度
            long fileSize = fis.getChannel().size();

            // 发送文件信息
            out.write(("File size: " + fileSize).getBytes());

            byte[] buffer = new byte[1024];
            int bytesRead;

            // 逐块发送文件内容
            while ((bytesRead = fis.read(buffer)) != -1) {
                out.write(buffer, 0, bytesRead);
            }

            // 关闭流
            fis.close();
            out.flush();

            // 接收服务器的反馈
            System.out.println(new String(in.readAllBytes()));

        } finally {
            socket.close(); // 关闭连接
        }
    }
}

**服务器（Server.java）：**

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

public class Server {
    private ServerSocket serverSocket;
    private Thread listenerThread;

    public Server(int port) {
        try {
            serverSocket = new ServerSocket(port);
            listenerThread = new ListenerThread(serverSocket);
            listenerThread.start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private class ListenerThread extends Thread {
        private Socket clientSocket;

        public ListenerThread(ServerSocket ss) {
            this.clientSocket = null;
            setDaemon(true);
        }

        @Override
        public void run() {
            try {
                clientSocket = ss.accept();
                handleConnection(clientSocket);
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (clientSocket != null) {
                    try {
                        clientSocket.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }

        private void handleConnection(Socket socket) {
            try (BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                 PrintWriter out = new PrintWriter(socket.getOutputStream(), true)) {

                // 接收文件大小信息
                String fileSizeStr = in.readLine();
                long fileSize = Long.parseLong(fileSizeStr.substring("File size: ".length()));

                // 检查是否成功接收
                byte[] buffer = new byte[(int) fileSize];
                int receivedBytes = 0;
                while (receivedBytes < fileSize) {
                    receivedBytes += in.read(buffer, receivedBytes, (buffer.length - receivedBytes));
                }

                // 存储或处理接收到的文件
                File outputFile = new File("receivedImg.jpg");
                FileOutputStream fos = new FileOutputStream(outputFile);
                fos.write(buffer);
                fos.close();

                // 发送确认信息给客户端
                out.println("File uploaded successfully!");

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        new Server(8080); // 假定服务器监听8080端口
    }
}