I'm doing a command nmap -sP <ip address> /24 every 20 seconds.
Then filtering out for the devices via a switch node.
This (filtered) message then goes into a trigger node with a 60 seconds timeout.
The 60 is what it has been increased to recently for the reason I shall now explain.
And then another couple of nodes before displaying the status.
One of the nodes is a function node that can change the name displayed.
By default it shows the IP address (last digit) and if a special message is sent to the devices they broadcast their name and the name is displayed rather than the IP number.
(Side note)
The device is an arduino node MCU via wifi.
I've been told/heard that that kind of chip is not reliable on WiFi connections. (end side note)
Time and time again I force the name to be displayed and in a shortish amount of time, it falls back to the IP number.
This happens if the trigger times out and shows the device as not connected.
Sod's law has it that as I am typing this: things won't go wrong.
But what I've seen is that the nmap command is sent but ONLY the WAP replies and not the device.
So is this because of the poor WiFi on the node MCU or ...... something else?
Yeah, kinda rhetorical, but if I don't ask...... Sod's other law will apply.
Yeah, I got around that problem - to call it a problem - a different way.
Originally I didn't use nmap. It was more a complicated ping and the ping response was used.
But as my network grew and other things, adding to the ping list became too tedious.
Though I do have to do a similar thing with nmap at least it is a bit more structured and is easily expanded as I add new devices.
So I send a command via MQTT and the device broadcasts its name and that is detected, stored in the function node and so when the device is saying I'm alive rather than sending the last bit of the IP address, the name is sent.
But once/if the trigger node times out, the device is marked as OFF LINE and so subsequent times when it is back on line it falls back to the IP address.
I am still not sure why I am doing this, but if the network needs to be ... rescanned (?) or the machine that is doing this is restarted all things are set back to default.
It just interests me why this is happening.
I've seen a few replies after sending the MQTT command to tell the device to broadcast it's name only return the WAP IP address from the nmap command and then some time later, the device does show up.
So I'm just not sure what is going on.
UPDATE
(Gotta be lucky)
With no known things happening this shows how it fails.
