java使用Socket实现TCP协议的excel文件从服务器下载到本机将其作为一个类写出并将下载后，基于字符流的文件写入存储作为一个类单独写出

在Java中，我们可以使用`java.net.Socket`类配合`java.io`包中的`InputStream`和`OutputStream`来实现实时TCP通信，并下载Excel文件。这里我会为你提供两个基本步骤的简化版代码示例：

1. **创建Server端** (用于接收请求并发送文件):

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class FileServer {
    private ServerSocket serverSocket;

    public void startServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
        System.out.println("Server started on port " + port);

        while (true) {
            Socket clientSocket = serverSocket.accept();
            try (BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                 PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true)) {

                String fileName = in.readLine(); // 接收文件名
                sendFile(clientSocket, fileName); // 发送文件

            } finally {
                clientSocket.close();
            }
        }
    }

    private void sendFile(Socket socket, String fileName) throws IOException {
        File file = new File(fileName);
        FileInputStream fis = new FileInputStream(file);
        byte[] buffer = new byte[4096];
        int bytesRead;

        while ((bytesRead = fis.read(buffer)) != -1) {
            socket.getOutputStream().write(buffer, 0, bytesRead);
        }
        fis.close();
        socket.close();
    }

    // ...其他停止服务的操作...
}

2. **创建Client端** (用于发起连接并下载文件):

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

public class FileClient {
    public static void main(String[] args) {
        try {
            String serverAddress = "localhost";
            int serverPort = 8000; // 修改为你服务器的实际端口
            Socket socket = new Socket(serverAddress, serverPort);
            
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            String fileName = "your_excel_file.xlsx"; // 修改为你想要下载的文件名
            
            // 请求文件
            out.println(fileName);
            File targetFile = new File(fileName);
            FileOutputStream fos = new FileOutputStream(targetFile);

            // 写入文件内容
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = socket.getInputStream().read(buffer)) != -1) {
                fos.write(buffer, 0, bytesRead);
            }

            fos.close();
            in.close();
            out.close();
            socket.close();

            System.out.println("Download complete.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这两个类分别实现了服务器端接收请求、发送文件和客户端请求文件、保存文件的功能。注意实际部署时，你需要处理异常并添加适当的错误处理。