feat: simple ws server impl

Cargo.toml

@@ -10,9 +10,20 @@ name = "mmp-port"
 path = "src/port/main.rs"
 required-features = ["port"]
 
+[[bin]]
+name = "mmp-server"
+path = "src/server/main.rs"
+required-features = ["server"]
+
 [dependencies]
 midi-msg = { version = "0.7", optional = true }
 midir = { version = "0.10", optional = true }
+tokio = { version = "1.41", features = ["net", "rt", "macros", "sync"], optional = true }
+tokio-tungstenite = { version = "0.24", optional = true }
+futures-util = { version = "0.3", optional = true }
+serde_json = { version = "1.0", optional = true }
+
 [features]
 default = []
 port = ["dep:midi-msg", "dep:midir"]
+server = ["dep:tokio", "dep:tokio-tungstenite", "dep:futures-util", "dep:serde_json"]

src/server/main.rs

@@ -0,0 +1,64 @@
+use std::{env, io::Error};
+
+use futures_util::TryStreamExt;
+use tokio::{io::AsyncWriteExt, net::{TcpListener, TcpStream}, sync::mpsc};
+
+#[tokio::main(flavor = "current_thread")]
+async fn main() -> Result<(), Error> {
+	let addr = env::args().nth(1).unwrap_or_else(|| "127.0.0.1:64080".to_string());
+	let addr2 = env::args().nth(2).unwrap_or_else(|| "0.0.0.0:60080".to_string());
+
+	let listener = TcpListener::bind(&addr).await.unwrap();
+	println!("Listening on: {}", addr);
+
+	let (tx, mut rx) = mpsc::unbounded_channel::<[u8;2]>();
+
+	tokio::spawn(async move {
+		let control_socket = TcpListener::bind(&addr2).await.unwrap();
+		while let Ok((mut stream, addr)) = control_socket.accept().await {
+			// don't spawn a new task: we only serve controls to one user at a time
+			println!("user {addr} connected, sending control signals...");
+			while let Some([ctrl, val]) = rx.recv().await {
+				if let Err(e) = stream.write_all(&[ctrl, val]).await {
+					eprintln!("error sending control, disconnecting -- {e}");
+					break;
+				}
+			}
+		}
+	});
+
+	while let Ok((stream, _)) = listener.accept().await {
+		tokio::spawn(accept_connection(stream, tx.clone()));
+	}
+
+	Ok(())
+}
+
+async fn accept_connection(stream: TcpStream, tx: mpsc::UnboundedSender<[u8;2]>) {
+	let addr = stream.peer_addr().expect("connected streams should have a peer address");
+	println!("Peer address: {}", addr);
+
+	let mut ws_stream = tokio_tungstenite::accept_async(stream)
+		.await
+		.expect("Error during the websocket handshake occurred");
+
+	println!("New WebSocket connection: {}", addr);
+
+	loop {
+		match ws_stream.try_next().await {
+			Err(e) => break eprintln!("user {addr} disconnected with error: {e}"),
+			Ok(None) => break println!("user {addr} disconnected"),
+			Ok(Some(msg)) => match msg {
+				tokio_tungstenite::tungstenite::Message::Text(txt) => {
+					let Ok([cmd, val]) = serde_json::from_str::<[u8;2]>(&txt) else {
+						break eprintln!("invalid websocket command: {txt}");
+					};
+					if let Err(e) = tx.send([cmd, val]) {
+						eprintln!("control channel is dead!");
+					}
+				},
+				m => eprintln!("unexpected message: {m:?}"),
+			},
+		}
+	}
+}