How do you intiiate communication from Native with flutter platform channels

Question

For our flutter to native communication, we are using platform channels as documented by google. We created a plugin package from the template and modifying it for our needs. Now there are some instances where the communication has to be invoked from the native layer. For example, image finished uploading and we need to send that back to flutter side.

There is no method channel on the Android/iOS side that can trigger this event.

There are couple of lines that mention this but the package itself is pretty big. Can some one help me understand how does this work. Thanks!

Note: A colleague figured out a way by using event channels but that seemed similar to a websocket and might be more performance hit?