def session_callback(self, signal):
        """Signalling from stream session.

        Data - new data available for processing.
        Playing - Connection is healthy.
        Retry - if there is no connection to device.
        """
        if signal == SIGNAL_DATA:
            self.event.new_event(self.data)

        elif signal == SIGNAL_FAILED:
            self.retry()

        if signal in [SIGNAL_PLAYING, SIGNAL_FAILED] and \
                self.connection_status_callback:
            self.connection_status_callback(signal)
Signalling from stream session.

        Data - new data available for processing.
        Playing - Connection is healthy.
        Retry - if there is no connection to device.