title: guacamole not able to connect neither VNC nor RDP
body: <p>I setup a guacamole server on ubuntu 16.04 Tried to setup a connection to a vnc server on the same machine and always got errors. I tried with RealVNC Xvnc11 TIghtVNC, and even with RDP. no luck. The error messages on log files were:</p>
  
  <pre><code>Creation of WebSocket tunnel to guacd failed: Non-numeric character in element length.
  
  Creation of WebSocket tunnel to guacd failed: java.net.ConnectException: 
  
  Connection refused (Connection refused)
  
  An internal error has occurred within the Guacamole server
  
  not a valid RFB client
  
  webSocketsHandshake: invalid client header
  </code></pre>
  
  <p>Any idea what could be?</p>