How to receive data from an Iframe in Dart?

I know that the only way to communicate with an iframe is using the postMessage method as follow:

iframe.contentWindow.postMessage("my message", window.location.href);

but I would like to know how to receive data from the iframe after any change on it.

Solution

In the receiver window, when you receive the message, you get the sender passed with the message and you can send back to this sender.

window.onMessage.listen((e) {
  e.source.postMessage({'somedata': 'xxx'}, '*');
});