用Nodejs写一个 HTTP/206 下载

下面是一个简单的 Node.js HTTP/206 下载示例：

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

const file = 'path/to/file'
const stat = fs.statSync(file)
const fileSize = stat.size

const server = http.createServer((req, res) => {
  const range = req.headers.range
  if (range) {
    const parts = range.replace(/bytes=/, '').split('-')
    const start = parseInt(parts[0], 10)
    const end = parts[1] ? parseInt(parts[1], 10) : fileSize - 1
    const chunksize = (end - start) + 1
    const fileStream = fs.createReadStream(file, { start, end })
    const headers = {
      'Content-Range': `bytes ${start}-${end}/${fileSize}`,
      'Accept-Ranges': 'bytes',
      'Content-Length': chunksize,
      'Content-Type': 'video/mp4'
    }
    res.writeHead(206, headers)
    fileStream.pipe(res)
  } else {
    const headers = {
      'Content-Length': fileSize,
      'Content-Type': 'video/mp4'
    }
    res.writeHead(200, headers)
    fs.createReadStream(file).pipe(res)
  }
})

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

这个示例代码会启动一个 HTTP 服务器，监听 3000 端口，当客户端请求视频资源时，会返回对应的 HTTP/206 响应，支持断点续传。