String Serial

int led = 13;

String stringLida = String(128);

void setup() {

  Serial.begin(9600);
  pinMode(led,OUTPUT);

}

void loop() {

  if(Serial.available()) {

    while (Serial.available()>0){
      char serial = Serial.read();
      stringLida += serial;
      delay(10);
    }
    Serial.println(stringLida);
  }

    if(stringLida == "liga")
    {
      digitalWrite(led, HIGH);
    }
    if(stringLida == "desliga")
    {
      digitalWrite(led, LOW);
    }
    stringLida = "";
}