Sending push in app is simple. App provide unique Device Token, then you call a POST from Node-RED sending message to this Token. Voila, device gets message directly from Node-RED.

Device token


Flows for Node-RED

To send push to app, you need to call a POST to 'https://fcm.googleapis.com/fcm/send' with a required json object.  Below flow has a function node to prepare JSON for POST node. Edit function node to modify title and body as you want



Note: Don't modify header object in function node!

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