Controlling LED with Android

#include <SoftwareSerial.h>

SoftwareSerial bluetooth(2, 3);  // RX, TX
const int lampPin = 13;  
char receivedChar;

void setup() {
  pinMode(lampPin, OUTPUT);
  bluetooth.begin(9600);
  Serial.begin(9600);
  Serial.println("منتظر دریافت دستور...");
}

void loop() {
  if (bluetooth.available()) {
    receivedChar = bluetooth.read();
    Serial.print("دستور دریافت شد: ");
    Serial.println(receivedChar);

    if (receivedChar == 'a') {
      digitalWrite(lampPin, HIGH);  
      Serial.println("لامپ روشن شد.");
    } 
    else if (receivedChar == 'b') {
      digitalWrite(lampPin, LOW);  
      Serial.println("لامپ خاموش شد.");
    }
  }
}