iOS 14 gives "OS Error: Bad file descriptor, errno = 9" when doing local network broadcasting

Question

I'm developing an app in Flutter that uses the udp package for broadcasting on the local network. This has worked fine on Android, Windows, macOS and iOS until I tried on an iOS 14.6 device.

The code flow is mainly like this:

var endPoint = Endpoint.broadcast(port: Port(6000));
var udpFuture = UDP.bind(Endpoint.any(port: Port(6000)));
udpFuture.then((udp) {
   udp.listen((datagram) {
       handleMessage(datagram.data);
   });
   udp.send(bytesToSend, endPoint);
}

The error message I'm getting is this: Unhandled Exception: OS Error: Bad file descriptor, errno = 9

user_467650 · Answer

Starting from iOS 14 your app needs the Multicast networking entitlement com.apple.developer.networking.multicast to be able to send or receive IP multicast traffic.

To get the entitlement you need to apply using Apple's request form. It took me 4-5 days before I got the request approved.

Then you can follow the instructions on Apple's forums to get up and running.

iOS 14 gives "OS Error: Bad file descriptor, errno = 9" when doing local network broadcasting

1 Answers