Wirelessly Control arduino output with other arduino

as topic, I need to control an appliance relay whenever a second arduino input located in another room goes HIGH.

I don't want to use public network IOT solutions like blynk or catenne,no nrf24 modules but rather using a wifi esp8266 communication. I don't want the system to go KO whenever connection is absent

What options do I have?

Please describe the entire project. You might be over thinking the need. There are receivers capable of triggering a relay. Why do you think you need 2 Arduinos. Let alone one?

How far apart are the two Arduinos? What sort of building infrastructure is between them? (The type of walls, etc can affect radio signals).

2.4GHz wireless with nR24L01+ modules should work if the distance is short. I have had it working between rooms in a brick-built building at a range of about 10 to 12 metres - I was not doing a range check so I have no idea what the limits might have been.

Wireless that works at 433MHz will have better penetration and range - such as the HC12 modules.

...R Simple nRF24L01+ Tutorial

One Arduino is located in ground g Floor, and second is outside the first floor. I'd say they're 60 feet one from the other and there are two walls. But the router is in the middle. I need to add an incompatible alarm (located outside) to my alarm box. I've located 2 high logic levels, one when the alarm is on, and one when the siren should go off. I'd like to associate these statuses to my homebuilt siren

I don’t think there is any option but to get some equipment and do some experiments.

And, sorry, I misread your Original Post - I did not see the “no” before nRF24

You could try direct communication between two ESP8266 modules using the ESP-NOW capability

…R

Interesting, thanks! I will definitely do some research about this espnow. This would even work in case my router breaks

I've tried to compile some example code but I keep getting this error:

Espnow.h not found... I've reinstalled my 2.4.2 community esp8266, and also tried a few manual patches that involved modding the .h and platform.txt but to no avail....help?

joerack: I've tried to compile some example code but I keep getting this error:

Espnow.h not found...

In my code I believe it is espnow.h. Case matters.

...R