#define ledPin 9
int state = 0;

void setup() {
 pinMode(ledPin, OUTPUT);
 digitalWrite(ledPin, LOW);
 Serial.begin(9600); 
}

void loop() {
 if(Serial.available() > 0){ // Checks if data is comming from the serial
 state = Serial.read(); // Reads the data from the serial port
 }
 
 if (state == '0') {
 digitalWrite(ledPin, LOW); // Turn LED OFF
 Serial.println("LED: OFF"); // Send back, to the phone, the String "LED: OFF"
 state = 0;
 }
 
 else if (state == '1') {
 digitalWrite(ledPin, HIGH);// Turn LED ON
 Serial.println("LED: ON");// Send back, to the phone, the String "LED: ON"
 state = 0;
 } 
}