#define pinLaser 2
#define pinReceiver 3
#define pinLED 4   // yellow
#define pinWSTrigger 5 // use to trigger Web Server

void setup() {
  Serial.begin(9600);
  pinMode(pinLaser, OUTPUT);
  pinMode(pinReceiver, INPUT);
  digitalWrite(pinLaser, HIGH);
  pinMode(pinLED, OUTPUT);
  digitalWrite(pinLED, LOW);
  pinMode(pinWSTrigger, OUTPUT);
  digitalWrite(pinWSTrigger, LOW);
}

void loop() {
  bool value = digitalRead(pinReceiver);
  //simulation only--
  value = true; // true: broken laser beam
  ///////////////////
  Serial.print("receiver value: ");
  Serial.println(value);
  //0: broken laser line (door state OPENED)
  //1: no broken line (door state CLOSED)
  // highlight LED when broken laser line
  digitalWrite(pinLED, value);
  // refresh trigger pin value
  digitalWrite(pinWSTrigger, value);
  delay(500);
}