stop method
Implementation
Future<void> stop() async {
await _subscription?.cancel();
_subscription = null;
_heartbeat?.cancel();
_heartbeat = null;
for (final client in _clients.toList()) {
try {
await client.close();
} catch (_) {}
}
_clients.clear();
_clientWatch.clear();
await _server?.close(force: true);
_server = null;
}