Arduino GPIO pin status

Hi, im new in this mit app inventor, i wanna ask on how to make an apps that can update my arduino pin status on my apps, for example if on my arduino for pin 10 turn off it will automatically update on the apps.

I'm not an expert in Arduino, but have you tried the Serial component? I've seen Arduino extensions in Pura Vida Apps:

You could make a simple web server on an arduino or esp32 board (still uses arduino pins and code, just with added features such as Bluetooth and WiFi antenna) then you can simply transmit the data via a Web server or over Bluetooth which can be read by the app. With this method you can manually control the pins status from the app as well.

If you want to use the arduino serial component you will need to have the phone/device connected over a USB cable and have your phones USB media settings set to allow the transfer of data. This will work but again depends on what you want to use this for, because having it plugged in to check isn't the most convenient.

it is possible to have one web server that can control multiple arduino?

I quite new to playing around with web servers so I am not 100% sure. If I had to guess I would say yes you can. Look at the esp32 simple Web server code/tutorial for ideas.

I would use MQTT. There are MQTT extensions, free servers, and libraries for arduino or esp.

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Didn't know about MQTT, look at this for examples ESP32. MQTT. Broker. Publish. Subscribe. ThingSpeak

Thanks to Ulli's extensions and arduino libraries, it's a very simple way to communicate. In addition, with the help of, for example, Rassbery, you should start your own broker.

So if i use MQTT, i need internet connection in order to control the arduino?

If you want to control an arduino while being far from the arduino then yes. But if arduino is close, all you need is a shared wifi network, not necessarily an internet connection. If you want to be offline you need a broker in your local network. You can do it on Rassbery or, for example, on an android phone.

Here an app and two Arduino with Bluetooth HC-06: