[FIXED] Flutter/Dart UDP multicast send from iOS not receiving on Android

Issue

With this setup, I've been able to get two android phones to send and receive UDP broadcasts. I can also use this setup to send a UDP broadcast from a physical Android device to an iPhone.

However, my problem is that it doesn't seem to work the other way around. The send function is ran on the iPhone, and the receive function is being run on the Android phone. The Android phone never gets the broadcast. It seems like something is wrong with the iPhone's sending function. Here's the setup:

The Android side that has worked for me before:

const port = 37069;
const address = '224.0.0.1';

void receive() async {
    final socket = await RawDatagramSocket.bind(address, port);
    socket.multicastHops = 1;
    socket.broadcastEnabled = true;
    socket.writeEventsEnabled = true;
    socket.listen((RawSocketEvent event) {
      print("still listening...");

      final packet = socket.receive();
      print("The packet was $packet");
      print("It came from ${packet?.address}");
    });
  }

and this is the iPhone side, that seems to be the problem. I'm not getting errors, so I'm wondering if there are any permissions in the Info.plist file that need to be added?

void broadcast() {
    // for the iphone
    RawDatagramSocket.bind(address, port).then((RawDatagramSocket socket) {
      socket.multicastLoopback = false;
      socket.broadcastEnabled = true;
      socket.readEventsEnabled = true;
      for (int i = 0; i < 150; i++) {
        socket.send("Sent #$i".codeUnits, InternetAddress(address), port);
        print("sent $i");
      }
      socket.close();
    });
  }

I've tested this same setup in my project, and it has worked in the following situations:

1. Android -> Android
2. Android -> iOS

but, iOS -> Android doesn't work. When I run the app, I can see that the iPhone is indeed sending the data, but the Android isn't receiving anything. Is the Android side the problem? What am I doing wrong?

Solution

I ended up using a package called Bonsoir to achieve what I wanted to. It lets you broadcast and receive network services, and I'm pretty sure its the same underlying technology as household programs like Airplay and Google Casting. It's also very reliable and simple to use.

To send a certain string, I passed in a string argument in the form of a dictionary into the attributes attribute within the BonsoirService class.

The package can be found here.

Answered By - Zachary Haslam
Answer Checked By - Marilyn (JavaFixing Volunteer)