Send notification to LAN devices (Android, Iphone) even when internet is down

Hello,

I have a running server (windows) with Node-red which send me various notification to connected devices via WhatsApp and emails thru Internet. I need to receive those notification in case of internet is down, while connected devices (Andorid, Iphone and so) are in the same network as the server (same LAN). Controlling node-red is working in this scenario because I'm connecting directly to Node-red Lan IP address, but notifications from Node-red are not working.
I need to receive those notification even when I'm sleeping and the phone screen is off (internet down).

Is it possible? Any advice?

Thanks.
Bob

On android you can use tasker or automate, there is a network plugin that can receive http request , or there are mqtt plugins. Nevers used an Iphone so can not help there.

Many people use a silent mode overnight to prevent notifications till the morning so watch out for that. Also, if the phone isn't plugged into power (and possibly even if it is), the power-saving modes of the phone may limit notifications depending on settings.

A different approach would be to use either a microprocessor device or a Raspberry Pi with a light/buzzer.