protected void sendChannelDisconectEvent() {
        logger.trace("Channel was not created, firing DisconnectEvent Event");
        // Send an event to the pipeline telling the Protocol filters what's going on.
        channel.pipeline().fireUserEventTriggered(new DisconnectEvent());
    }
Subscriptions are only supported in a small subset of the S7 devices.

@return true, if the device supports subscriptions.
plc4j/drivers/s7/src/main/java/org/apache/plc4x/java/s7/readwrite/protocol/S7HPlcConnection.java