getNtpOffset static method

Implementation

static Future<int?> getNtpOffset({
  String lookUpAddress = _defaultLookup,
  int port = 123,
  DateTime? localTime,
  Duration? timeout,
}) async {
  timeout = timeout ?? Duration(seconds: 40);
  try {
    final List<InternetAddress> addresses = await InternetAddress.lookup(
      lookUpAddress,
    );

    if (addresses.isEmpty) {
      debugPrint('❌ Could not resolve address for $lookUpAddress.');
      return null;
    }

    final InternetAddress serverAddress = addresses.first;
    InternetAddress clientAddress = InternetAddress.anyIPv4;
    if (serverAddress.type == InternetAddressType.IPv6) {
      clientAddress = InternetAddress.anyIPv6;
    }

    // Init datagram socket to anyIPv4 and to port 0
    final RawDatagramSocket datagramSocket = await RawDatagramSocket.bind(
      clientAddress,
      0,
    );

    final _TrueTimeProviderMessage ntpMessage = _TrueTimeProviderMessage();
    final List<int> buffer = ntpMessage.toByteArray();
    final DateTime time = localTime ?? DateTime.now();
    ntpMessage.encodeTimestamp(
      buffer,
      40,
      (time.millisecondsSinceEpoch / 1000.0) + ntpMessage.timeToUtc,
    );

    // Send buffer packet to the address [serverAddress] and port [port]
    datagramSocket.send(buffer, serverAddress, port);

    Datagram? packet;

    bool receivePacket(RawSocketEvent event) {
      if (event == RawSocketEvent.read) {
        packet = datagramSocket.receive();
      }
      return packet != null;
    }

    try {
      await datagramSocket.timeout(timeout).firstWhere(receivePacket);
    } catch (e) {
      debugPrint("⚠️ Timeout or receive error: $e");
      return null;
    } finally {
      datagramSocket.close();
    }

    if (packet == null) {
      debugPrint("⚠️ NTP fetch failed: Received empty response.");
      return null;
    }

    final int offset = _parseData(packet!.data, DateTime.now());
    return offset;
  } catch (e) {
    debugPrint("❌ NTP fetch failed with error: $e");
    return null;
  }
}