This is a function that a Dart Isolate can execute. It will listen for messages from the main thread and also send messages to the main thread.

isolate-function.dart

void myIsolate(SendPort isolateToMainStream) {
  ReceivePort mainToIsolateStream = ReceivePort();
  isolateToMainStream.send(mainToIsolateStream.sendPort);

  mainToIsolateStream.listen((data) {
    print('[mainToIsolateStream] $data');
  });

  isolateToMainStream.send('This is from myIsolate()');
}