server: Parse messages

[tattlekey] / server / src / main.rs

diff --git a/server/src/main.rs b/server/src/main.rs
index e7a11a969c037e00a796aafeff6258501ec15e9a..c4c0b19c07f9587a80090e2ea45f7944b6984abc 100644 (file)
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -1,3 +1,73 @@
+// tattlekey: A one-key UDP keyboard
+// Copyright (C) 2023  Scott Worley <scottworley@scottworley.com>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+use std::net::UdpSocket;
+
+const MESSAGE_SIZE: usize = 12;
+
+#[derive(Debug)]
+struct MessageKey {
+    epoch: u32,
+    device: u16,
+    seq: u16,
+}
+
+#[derive(Debug)]
+struct Message {
+    key: MessageKey,
+    ago: u32,
+}
+
+impl From<&[u8; MESSAGE_SIZE]> for Message {
+    fn from(value: &[u8; MESSAGE_SIZE]) -> Self {
+        Self {
+            key: MessageKey {
+                epoch: u32::from_be_bytes(value[0..=3].try_into().expect("I can't count")),
+                device: u16::from_be_bytes(value[4..=5].try_into().expect("I can't count")),
+                seq: u16::from_be_bytes(value[6..=7].try_into().expect("I can't count")),
+            },
+            ago: u32::from_be_bytes(value[8..=11].try_into().expect("I can't count")),
+        }
+    }
+}
+impl TryFrom<&[u8]> for Message {
+    type Error = std::array::TryFromSliceError;
+    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+        match <[u8; MESSAGE_SIZE]>::try_from(value) {
+            Ok(correct_size) => Ok(Message::from(&correct_size)),
+            Err(e) => Err(e),
+        }
+    }
+}
+
 fn main() {
-    println!("Hello, world!");
+    let socket = UdpSocket::bind("0.0.0.0:29803").expect("couldn't bind to address");
+    loop {
+        let mut buf = [0; MESSAGE_SIZE];
+        match socket.recv_from(&mut buf) {
+            Err(e) => eprintln!("Didn't receive data: {e}"),
+            Ok((number_of_bytes, src_addr)) => {
+                let filled_buf = &buf[..number_of_bytes];
+                if number_of_bytes != MESSAGE_SIZE {
+                    eprintln!("Ignoring short message ({number_of_bytes}) from {src_addr}");
+                    continue;
+                }
+                let message = Message::try_from(filled_buf).expect("I can't count");
+                println!("Got packet from {src_addr}: {message:?}");
+            }
+        }
+    }
 }