title: Making IPv4 request IP use IPv4 notation instead of IPv6
body: <p>Express <a href="https://stackoverflow.com/questions/10849687/express-js-how-to-get-remote-client-address">provides the request IP address via <code>req.ip</code></a> (where <code>req</code> is the request), but for IPv4 addresses it uses <a href="https://stackoverflow.com/questions/5861107/when-is-the-hybrid-ip-notation-ffff192-168-1-4-appropriate">IPv6 notation</a>, e.g.:</p>
  
  <pre><code>::ffff:1.2.3.4
  </code></pre>
  
  <p>I'm happy that it supports IPv6 with no fuss, but for UI purposes I'd like to display IPv4 addresses in IPv4 notation ("1.2.3.4") while, of course, still maintaining support for IPv6 addresses.</p>
  
  <p>Can I get Express to use pure IPv4 notation for IPv4 request addresses?</p>