stop method
Stops the agents, closes every socket and the listener.
Implementation
Future<void> stop() async {
if (_stopped) return;
_stopped = true;
for (final a in _agents) {
a.detach();
}
faults.cancelTimers();
await gateway.close();
await terminalStreams.close();
await _http.close(force: true);
await Future.wait(List.of(_serving));
}