title: Django get client's domain name/host name
body: <p>What is the easiest way to obtain the user's host/domain name, if available?
  Or is there a function to lookup the IP address of the user to see if it is bound to a named address? (i.e. gethostbyaddr() in PHP)</p>
  
  <p>HttpRequest.get_host() only returns the IP address of the user.</p>