Arduino-Unity Serial (Arduino side)

int buttonPin = 2;
int buttonState = LOW;

void setup() {
  Serial.begin(9600);
  pinMode(buttonPin, INPUT);
}

void loop() {
  /*
  if (Serial.read() == '1')
  {
    digitalWrite(ledPin, HIGH);
  }
  if (Serial.read() == '2')
  {
    digitalWrite(ledPin, LOW);
  }
*/
buttonState = digitalRead(buttonPin);
 if (buttonState == HIGH)
 {
Serial.println("1");

Serial.flush();
 }
else
{
Serial.println("0");

Serial.flush();
}


}