main.dart

import 'dart:async';

void main() {
  StreamController<int> controller = new StreamController<int>();
  
  var stream = controller.stream.asBroadcastStream();
  var sink = controller.sink;
  
  sink.add(1);
  
  stream.listen((v) => print(v));
  
  sink.add(2);
  
  stream.listen((v) => print(v));
}

import 'dart:async';

void main() {
  StreamController<int> controller = new StreamController<int>.broadcast(sync: true);

  var stream = controller.stream;
  var sink = controller.sink;

  sink.add(1);

  stream.listen((v) => print('First: $v'));

  sink.add(2);

  Future.delayed(Duration(seconds: 1), () {
    stream.listen((v) => print('Second: $v'));
  });
  
  stream.listen((v) => print('Third: $v'));
}