title: How to find out which process is using localhost:80?
body: <p>I'm using linux mint xfce edition, my localhost:80 was used by some program but I don't which one, when I open firefox and visit localhost:80, it says </p>
  
  <p><em>It works!
  This is the default web page for this server.
  The web server software is running but no content has been added, yet.</em></p>
  
  <p>I've tried to use <code>lsof -i @localhost:80</code>, but it returns nothing. </p>