title: Facebook exchange code for token
body: <p>When you successfully exchange a "code" for a token</p>
  
  <p>facebook responses with the following (html body)</p>
  
  <pre><code> access_token=USER_ACCESS_TOKEN&amp;expires=NUMBER_OF_SECONDS_UNTIL_TOKEN_EXPIRES
  </code></pre>
  
  <p>But what happens when this code for token exchange fails? how does facebook response when the exchange fails?</p>
  
  <p><strong>Reference</strong> <a href="https://developers.facebook.com/docs/howtos/login/server-side-login/" rel="nofollow">https://developers.facebook.com/docs/howtos/login/server-side-login/</a></p>