title: Why is SockJS incompatible?
body: <p>My app works fine when sockjs is using the websocket protocol. But I am getting an error in the server:</p>
  
  <pre><code>Uncaught Error: Incompatibile SockJS! Main site uses: "1.3.0", the iframe: "1.0.0".
  </code></pre>
  
  <p>How can I debug this?</p>