What the most efficient way to build In-App messaging for ionic app

I spent the past two days looking for the concept behind sending rich in-app messages from server to ionic app without using service provider like appoxee.

Unfortunately, all my search end up with no useful information, and am still struggling is it done by GCM and APNs by send push notification and handle it with local notification seems wrong as i cant sent rich content, or its done by sending message from my server directly when event occur.

Did you ever land on anything here? Inquiring minds want to know.