git.scottworley.com Git - tattlekey/blob - server/src/main.rs

   1 // tattlekey: A one-key UDP keyboard
   2 // Copyright (C) 2023  Scott Worley <scottworley@scottworley.com>
   3 //
   4 // This program is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // This program is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
  16
  17 use std::net::UdpSocket;
  18 use std::time::{Duration, SystemTime};
  19
  20 const MESSAGE_SIZE: usize = 12;
  21
  22 #[derive(Debug)]
  23 struct MessageKey {
  24     epoch: u32,
  25     device: u16,
  26     seq: u16,
  27 }
  28
  29 #[derive(Debug)]
  30 struct Message {
  31     key: MessageKey,
  32     ago: u32,
  33     t: SystemTime,
  34 }
  35
  36 impl From<&[u8; MESSAGE_SIZE]> for Message {
  37     fn from(value: &[u8; MESSAGE_SIZE]) -> Self {
  38         let ago = u32::from_be_bytes(value[8..=11].try_into().expect("I can't count"));
  39         Self {
  40             key: MessageKey {
  41                 epoch: u32::from_be_bytes(value[0..=3].try_into().expect("I can't count")),
  42                 device: u16::from_be_bytes(value[4..=5].try_into().expect("I can't count")),
  43                 seq: u16::from_be_bytes(value[6..=7].try_into().expect("I can't count")),
  44             },
  45             ago,
  46             t: SystemTime::now() - Duration::new(ago.into(), 0),
  47         }
  48     }
  49 }
  50 impl TryFrom<&[u8]> for Message {
  51     type Error = std::array::TryFromSliceError;
  52     fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
  53         match <[u8; MESSAGE_SIZE]>::try_from(value) {
  54             Ok(correct_size) => Ok(Message::from(&correct_size)),
  55             Err(e) => Err(e),
  56         }
  57     }
  58 }
  59
  60 fn main() {
  61     let socket = UdpSocket::bind("0.0.0.0:29803").expect("couldn't bind to address");
  62     loop {
  63         let mut buf = [0; MESSAGE_SIZE];
  64         match socket.recv_from(&mut buf) {
  65             Err(e) => eprintln!("Didn't receive data: {e}"),
  66             Ok((number_of_bytes, src_addr)) => {
  67                 let filled_buf = &buf[..number_of_bytes];
  68                 if number_of_bytes != MESSAGE_SIZE {
  69                     eprintln!("Ignoring short message ({number_of_bytes}) from {src_addr}");
  70                     continue;
  71                 }
  72                 let message = Message::try_from(filled_buf).expect("I can't count");
  73                 println!("Got packet from {src_addr}: {message:?}");
  74             }
  75         }
  76     }
  77 }