Merge PR #6468: fix(photocraft): --control 0 logs the port actually bound (#6427)

apps/photocraft/src/control_server.rs

@@ -25,7 +25,7 @@ pub fn start(port: u16, token: String, ctx: egui::Context) -> Receiver<ControlRe
             return rx;
         }
     };
-    eprintln!("photocraft: control server listening on 127.0.0.1:{port}");
+    eprintln!("photocraft: control server listening on {}", listening_addr(&listener, port));
     std::thread::spawn(move || {
         let limiter = ConnectionLimiter::new(MAX_CONNECTIONS);
         let token = Arc::new(token);
@@ -47,6 +47,16 @@ pub fn start(port: u16, token: String, ctx: egui::Context) -> Receiver<ControlRe
     rx
 }
 
+/// The address `listener` is bound to: with `--control 0` the OS picks the port, and a client
+/// needs that one, not the requested 0 (#6427). Falls back to the requested port if the OS
+/// can't report it.
+fn listening_addr(listener: &TcpListener, requested_port: u16) -> String {
+    match listener.local_addr() {
+        Ok(addr) => addr.to_string(),
+        Err(_) => format!("127.0.0.1:{requested_port}"),
+    }
+}
+
 fn serve(stream: TcpStream, token: &str, tx: Sender<ControlRequest>, ctx: egui::Context) {
     serve_with_auth_deadline(stream, token, tx, ctx, AUTH_DEADLINE);
 }
@@ -131,6 +141,17 @@ mod tests {
     use super::*;
     use std::io::BufRead;
 
+    /// #6427: with port 0 the log names the port the OS bound, which a client can connect to.
+    #[test]
+    fn port_zero_logs_the_bound_port() {
+        let listener = TcpListener::bind(("127.0.0.1", 0)).unwrap();
+        let bound = listener.local_addr().unwrap();
+        assert_ne!(bound.port(), 0);
+        let logged = listening_addr(&listener, 0);
+        assert_eq!(logged, format!("127.0.0.1:{}", bound.port()));
+        TcpStream::connect(&logged).unwrap();
+    }
+
     /// #4965: a connection that keeps sending without authenticating is closed at the deadline
     /// (releasing its connection permit), and nothing it sent is dispatched.
     #[test]