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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.

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  • hmm. you could use sound. or older mobile phones have ir transmitters
    – Ewan
    Jun 13, 2017 at 23:24
  • IR transmitters can be blocked by objects in the environment, so I like the proximity aspect of Bluetooth. Sound is a novel idea and I like that but if someone uses the app in a car to hit a receiver outside, the sound might be lost.
    – Brian Errigo
    Jun 14, 2017 at 16:39
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    have you looked into the low energy bluetooth stuff? it has minimal handshaking
    – Ewan
    Jun 14, 2017 at 16:41
  • why am I at -1? what did I do?
    – Brian Errigo
    Jun 14, 2017 at 16:41
  • dunno, i voted you up
    – Ewan
    Jun 14, 2017 at 16:41

1 Answer 1

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Have you thought about sending a UDP packet to the PI over a network? UDP is unreliable, but it's very quick and doesn't require any handshakes. Further there is UDP support in most programming languages. If the PI is accessible on the internet, then your mobile phone can send this packet from anywhere in the world where it has data access. Or if you're only interested in local access, you can send the packet to the PI on the same wifi network the mobile phone is on.

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    You'll need a stable ip address on both sides.
    – Robert Harvey
    Jun 14, 2017 at 2:37
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    This doesn't help me because the two devices are not going to be on the same network, ever. And connecting to the pi as if it were a network would slow down the process to the point where it wasn't useful anymore
    – Brian Errigo
    Jun 14, 2017 at 16:38

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