当一个文件已经作为分块/表单数据从客户端上传时，如何从node.js发送该文件？

const http = require('http');
const fs = require('fs');

const server = http.createServer((req, res) => {
  if (req.method === 'POST' && req.url === '/upload') {
    // 处理文件上传请求
    const fileStream = fs.createWriteStream('uploaded_file.txt');

    req.on('data', (chunk) => {
      // 将接收到的数据写入文件流
      fileStream.write(chunk);
    });

    req.on('end', () => {
      // 数据接收完毕，关闭文件流
      fileStream.end();
      res.statusCode = 200;
      res.end('File uploaded successfully');
    });
  } else {
    res.statusCode = 404;
    res.end('Not found');
  }
});

server.listen(3000, () => {
  console.log('Server is running on port 3000');
});