the DHCP range is 172.20.10.X with iOS 6 and later
I bet if the broadcast packet was sent to the 172 network it would pick it right up.
That said, it would mean hardcoding the app... which as a programmer gives me the shivers.
There should be a way to find the subnet of the broadcasting hotspot and check it though.
I was going to give jakematic credit for steering me to those tools
and suggest the following:
-offer a user-configurable subnet to scan (defaulting to 172.20.10.xxx would be ideal, but as long as I can set-it-and-forget-it I'd be happy)
I've not tried playing with ifconfig or similar (my iPhone is jailbroken) to see, but I'd imagine there are well-defined networks corresponding to WiFi and Cellular. Whether Apple allows mere userland apps much access is another story
I tried hotspot first (well Ok, second - I did try WiFi to be sure it worked) because that's exactly the usage model that limited me in Germany
I foolishly (I was really busy, the dog ate my homework, etc) didn't try the setup in the US and then found in Germany that I didn't know the IP of the Hex-Net on my hotspot
Plus I could see this being a common "help a buddy" mode where I just use my own phone hotspot network to connect Hex-Net.
Richard