1. @override
StreamSubscription listen(void onData(event), { Function onError, void onDone(), bool cancelOnError: false })

Adds a listener for data events from other isolates.

When an isolate invokes add, all other isolates receive that data in onData.

onError, if provided, will be invoked when an isolate tries to add bad data. Only the isolate that failed to send the data will receive onError events.

Source 

@override
StreamSubscription<dynamic> listen(void onData(dynamic event),
    {Function onError, void onDone(), bool cancelOnError: false}) =>
  _inboundController.stream.listen(
      onData,
      onError: onError ?? (err, st) => _logger.severe("ApplicationMessageHub error", err, st),
      onDone: onDone,
      cancelOnError: cancelOnError);