// declare and initialize pin for LED
const int ledPin =  D8;// the number of the LED pin

String value;

// the setup function runs once when you press reset or power the board
void setup() {
	// initialize digital pin for LED as an output.
	pinMode(ledPin, OUTPUT);
	
	Serial.begin(9600); // Start serial communication
	while (!Serial); // Wait until Serial is open
	Serial.println("listening..."); // Send that Serial is open and listening
}

// the loop function runs over and over again forever
void loop() {
	if (Serial.available() > 0) {
		// read the incoming string
		value = Serial.readString();
		
		if (value == "1"){
			digitalWrite(ledPin, HIGH);   // turn the LED on
			Serial.println("Message '1' received. Turning LED on.");
		}
		else if (value == "0"){
			digitalWrite(ledPin, LOW);   // turn the LED off
			Serial.println("Message '0' received. Turning LED off.");
		}
		else {
			Serial.print("Unknown message '");
			Serial.print(value);
			Serial.println("'. Use '1' and '0' to turn LED on and off.");
		}
	}
}