@Override
            public void onMessage(String message) {
                GuacamoleWebSocketTunnelEndpoint.this.onMessage(message);
            }
Returns a new tunnel for the given session. How this tunnel is created
or retrieved is implementation-dependent.

@param session The session associated with the active WebSocket
               connection.
@param config Configuration information associated with the instance of
              the endpoint created for handling this single connection.
@return A connected tunnel, or null if no such tunnel exists.
@throws GuacamoleException If an error occurs while retrieving the
                           tunnel, or if access to the tunnel is denied.
guacamole-common/src/main/java/org/apache/guacamole/websocket/GuacamoleWebSocketTunnelEndpoint.java