int LED = 13;
String inputString = "";

void setup()
{  
  Serial.begin(9600);
  inputString.reserve(24);
  pinMode(LED, OUTPUT);
} 

void ReadSerial()
{
  char inChar;  
  while (Serial.available() > 0)
  {
    // get the new byte:
    inChar = Serial.read(); 
    
    // add it to the inputString:
    if ((inChar != 10) && (inChar != 13)) // '\n\r'
      inputString.concat(inChar);
    else
    {
      if (inputString.indexOf("hello") >= 0)
      {
        // return to OS3D
        Serial.println("arduino");
      }
      else if (inputString == "0" || inputString == "off")
      {
        digitalWrite(LED, LOW);
        
        // return to OS3D
        Serial.println("Led Off");
      }
      else if (inputString == "1" || inputString == "on")
      {
        digitalWrite(LED, HIGH);
        // return to OS3D
        Serial.println("Led On");
      }
      
      inputString = "";
    } 
  }
  Serial.flush();
}

void loop() 
{
  ReadSerial();
}