isVmServiceReachable function

Future<bool> isVmServiceReachable(String uri)

Returns true if the VM service at uri is reachable by opening a WebSocket and waiting for the first byte (or a clean open). Times out quickly so fdb status does not block for long when the app is truly dead.

This is used as a fallback by fdb status when the PID file is missing or points to a dead process — a common scenario when fdb launch was killed by an agent timeout after the app started but before APP_STARTED was printed.

Implementation

Future<bool> isVmServiceReachable(String uri) async {
  try {
    final ws = await WebSocket.connect(uri).timeout(const Duration(seconds: 3));
    unawaited(ws.close());
    return true;
  } catch (_) {
    // Intentional: timeout and all network errors mean "not reachable = false".
    // This probe function is an explicit exception to the general
    // "rethrow TimeoutException" rule — a timeout here is the probe's false case.
    return false;
  }
}