title: How do I avoid WebSocketHandshakeException: Requested subprotocol(s) not supported
body: <p>I am using websockets in the play framework.
  I would like to use a subprotocol, i.e. set the header Sec-WebSocket-Protocol to a protocol, which is not supported by jboss/Heroku:</p>
  
  <pre><code>org.jboss.netty.handler.codec.http.websocketx.WebSocketHandshakeException: Requested subprotocol(s) not supported
  </code></pre>
  
  <p>I am implementing the protocol I specify in Sec-WebSocket-Protocol, and for this reason the server should accept the sub-protocol.
  I run into this error even before I reach the first breakpoint in my code.
  Can I configure jboss/Heroku to accept the given sub protocol?
  And if so - how?</p>
  
  <p>Thanks,
  -Louise</p>