Configure flutter web app to broadcast data to any subscribed listeners with sse - flutter

Question

I am currently developing a flutter web app, and would like to implement a feature to broadcast json data to any listeners/subscribers.
To give more detail:
The web app has a flutter front end server running on localhost. A user will be able to fetch some JSON data from an external backend server using a simple GET request.
Once the app has loaded the JSON data, it will need to broadcast it down an SSE stream to any listeners. This listener will be a seperate flutter application.
Now, I understand that there a few problems with this.
Firstly, Flutter web doesn't support dart:io... Fine - I have managed to get round this by using the universal_io dart package instead of dart:io. The api is the same, and after solving a few CORS errors, works a charm for the GET requests in the first bullet above. This means that the json data can be successfully loaded into the Flutter app.
(universal_io dart package -> https://pub.dev/packages/universal_io).
The next issue is with SSE. Part one of this is that there is not much documentation on implementing an SSE server in Flutter - only a client that can listen. However, I have managed to find a solution in the sse dart package example app...
import 'package:shelf/shelf_io.dart' as io;
import 'package:sse/server/sse_handler.dart';
/// A basic server which sets up an SSE handler.
///
/// When a client connnects it will send a simple message and print the
/// response.
void main() async {
var handler = SseHandler(Uri.parse('/sseHandler'));
await io.serve(handler.handler, 'localhost', 0);
var connections = handler.connections;
while (await connections.hasNext) {
var connection = await connections.next;
connection.sink.add('foo');
connection.stream.listen(print);
}
}
(sse dart package -> https://pub.dev/packages/sse)
(continued) Usually, this would be a fine solution, and it could probably be modified a little for implementation within a flutter app. However, the shelf_io.dart package, used to spin up the server, depends on the dart:io package, which doesn't work with Flutter Web.
The other thought is - why do we need to set up a new server connection (with io.server(...)) when the flutter web app is already running on its own localhost server? This begs the question: Is there a way to add this sseHandler endpoint onto the localhost server that the Flutter Web app is running on?
All in all, what i'm trying to ask is:
Is there a way for a Flutter Web App to send SSE messages to a collection of listeners?
At the moment I've hit a bit of a deadend with research on this so if anyone had any bright ideas on a potential solution then the help would be greatly appreciated. Thanks :)
Side Note: Obviously this is something that could very easily be done with Java, J2Html and so on, but wheres the fun in giving up just like that... On the other hand, maybe flutter web is still just too new to support stuff like this?