@Override
    public void onWebSocketBinary(byte[] payload, int offset, int length) {
        throw new UnsupportedOperationException("Binary WebSocket messages are not supported.");
    }
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.
@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/src/main/java/org/apache/guacamole/tunnel/websocket/jetty9/GuacamoleWebSocketTunnelListener.java