title: How can you tell if a file is fully downloaded via HTTP?
body: <p>How can you tell if a file is fully downloaded via <code>HTTP</code>?</p>
  
  <p>What if you have flushed the packets from the server, but the user is still downloading them? Won't the <code>TCP FIN</code> packet look identical - whether the user has finished or has cancelled the download?</p>