I'm using a Ardeunis device which only sends data if any of the monitoring ports have changed and at least one 'Keep Alive Frame' every 24 hours so I can be sure the device is still alive.
What would you recommend as best approach to send an alarm if the device has not been 'seen' for more than 24 hours? My first approach was to handle each Keep Alive Frame combined with a timer. If the timer is overdue, lets say 25 hours, it will send an alarm.
But now my second idea is not only to use the Keep Alive Frames, but if any package is received, to set the epoch time in a file. Why a file? If I understood correctly, all variables get lost if the flow gets redeployed, right? So from that point of view a file containing just the epoch time of the last package seems to be a better way of storing this data.
Next, some kind of timer, or just a daily check at a fixed time for all epochs. For now I have just one device, but this single device will get company sooner or later
If you also wrote some kind of watchdog in your project and are willing to share, please let me know.