Currently I am working on a Schoolproject and I need to send a Notification to a self written Xamarin Forms App from my API. It all runs on a local network and the App can already communicate with the Api, now i want my api to send a notification to my phone if a specific event turns true. How do I do this? (Oh and I am using Python flask for my API, if u need this Information)
Use Push notification for it. As soon as there is a need to call
mobile app from web server send a push notification. Handle the push
notification on application side to make a call to web api as soon as
it receives the push notification with specific payload. 
Use Web Sockets if server events are too frequent.
How do I send a get request from my Api to a Xamarin forms app?