I'm looking for a way to send a signal between a raspberry pi and a smart phone. What I want to do is hash a few basic bits of information about the phone to use as a UUID. I then want to transmit that UUID wirelessly to the receiver (pi) and then have the pi send that data to my database to be verified.
For transmitting the data, I've done a bit of research but nothing seems to land right where I want it. I'd like to just push the button in my phone app, and then have the phone broadcast a "magic" packet that the receiver will be able to sniff out of the air. I don't want to waste time with hand shaking or connecting, I just want to send on command, and let the scanner pi try and sort it out.
So far I've tried using bluetooth, by changing the display name I can transmit strings of data which is enough, but waiting for the PI to pick up the bluetooth signal takes too long. I've been reading into constructing a custom data frame for wifi but as far as I can tell that only works for 'local' subnets, so I couldn't just arbitrarily listen for packets on the scanner pi. My last idea was NFC but i need some range on the transmission so NFC wont cut it.
If anyone has knowledge on how to better control these platforms I'd like to know, or if there's another technological platform I could use, I would appreciate the input.