title: How do I get the domain originating the request in express.js?
body: <p>I'm using express.js and I need to know the domain which is originating the call. This is the simple code</p>
  <pre><code>app.get(
      '/verify_license_key.json',
      function( req, res ) {
          // do something
  </code></pre>
  <p>How do I get the domain from the <code>req</code> or the <code>res</code> object?
  I mean I need to know if the API was called by <code>somesite.example</code> or <code>someothersite.example</code>.
  I tried doing a console.dir of both <code>req</code> and <code>res</code> but I got no idea from there, also read the documentation but it gave me no help.</p>