char nodo = 'b'; //nombre del nodo, letra que busca
                 //node name, letter you it's looking for

void setup()
{
  Serial.begin (9600);
  pinMode(13,OUTPUT);
}

void loop()
{
  if (Serial.read() == nodo)
  {
    digitalWrite (13,HIGH);
    delay(100); //este delay debe ser menor que el del master
                //this delay must be shorter than the master one
    Serial.println(" in loop");
  }
  else
  { //sino han publicado su letra,apaga el led
    //if it's letter hasn't been published, turn off the led
    digitalWrite (13,LOW);
    //delay (100);
  }
}