mDns error on iOS - error 49 Can't assign requested address

Question

I'm using the multicast_dns package for Flutter and get an exception on iOS.
It works as expected on Android. I have tested this with the code example provided with the package, see https://pub.dev/packages/multicast_dns

The error is:

OS Error: Can't assign requested address, errno = 49 in
_NativeSocket.joinMulticast. (socket_patch.dart)

I have tried various multicast addresses, the default 224.0.0.251, 230.180.0.1 and 239.0.180.1.

import 'package:multicast_dns/multicast_dns.dart';

Future<void> main() async {
  const String name = '_dartobservatory._tcp.local';
  final MDnsClient client = MDnsClient();
  await client.start(mDnsAddress: InternetAddress('239.0.180.1'));

  await for (PtrResourceRecord ptr in client
      .lookup<PtrResourceRecord>(ResourceRecordQuery.serverPointer(name))) {

    await for (SrvResourceRecord srv in client.lookup<SrvResourceRecord>(
        ResourceRecordQuery.service(ptr.domainName))) {
      final String bundleId =
          ptr.domainName; //.substring(0, ptr.domainName.indexOf('@'));
      print('Dart observatory instance found at '
          '${srv.target}:${srv.port} for "$bundleId".');
    }
  }
  client.stop();

  print('Done.');
}

Flutter doctor:

mdnstest $ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.9.1+hotfix.4, on Mac OS X 10.14.5 18F203, locale
    en)
 
[!] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    ✗ Android licenses not accepted.  To resolve this, run: flutter doctor
      --android-licenses
[✓] Xcode - develop for iOS and macOS (Xcode 11.0)
[✓] Android Studio (version 3.5)
[✓] Connected device (1 available)

! Doctor found issues in 1 category.