Based on another thread that was discussing presence detection, I decided to try to use my phone's WiFi connection to my OpenWRT router to update my Hubitat presence sensor. Not it's presence on the network via a ping, but a trigger based on the connection being made. Did I really need this? No. A ping sensor mostly does the same thing. But it was still an interesting exercise and now I have a method to push any event logged by my router to Hubitat if a need arises.
My presence sensing is pretty solid, but it glitches or rare occasion. I'm using the Hubitat Android app, OwnTracks, and Google Assistant to detect presence. On rare occasion they all fail because the phone simply doesn't update its location until it is awakened, so none of the apps see the location update.
I combine the 3 sensors with the Combined Presence app. That has an option to use a WiFi sensor to set presence (but not absence) using a ping sensor. My ping sensors are set to a 30 second interval, so triggering off the log event is up to 30 seconds faster than the ping sensor.
I added the 'node-red-contrib-syslog-input2' node to Node Red and set it up to listen on UDP port 20514. In OpenWRT, under System -> System -> Logging I set the external system log server to my Node Red IP, port 20514, UDP. I set the system log level to Info to reduce the message traffic - the default was Debug.
In Node Red I created a flow that starts with the Syslog node and then goes to a switch with two outputs. Output 1 is if the msg.payload.msg matches regex "DHCPACK.*xx:xx:xx:xx:xx:xx*" (set to my phone's MAC address). Output 2 is set up for if the msg.payload.msg matches my wife's MAC address.
If a log message matches, the next nodes are a Hubitat Device node and a switch node to check if the combined presence device's presence attribute is != present. If it isn't, the message passes to a Hubitat Command node that sets the combined sensor to 'present'.
The surprising thing is that I've already seen this flow activate several times in the first 24 hours it's been set up. I thought this would be a backup to the backup to the backup for presence sensing, but it may end up being the first sensor to detect arrivals a good fraction of the time.
I may disable the phone ping sensors since they could be up to 30 seconds slower than the log-based presence and would only provide redundancy if Node Red were down. If Node Red were down I'd have bigger problems than presence sensing as I'm using it for a lot of automation logic now.
