int ledPin = 13; 
int state = 0;
int flag = 0; 
#include <SoftwareSerial.h>
SoftwareSerial BTSerial(11,10);
 
void setup() {
 pinMode(ledPin, OUTPUT);
 digitalWrite(ledPin, LOW);
 Serial.begin(9600);
 BTSerial.begin(9600);
 while(!BTSerial);
 Serial.println("AT commands:okay");
  }

void loop() {
 if(BTSerial.available() > 0){
 state = BTSerial.read();
 flag=0;
 }
 if (state == '0') {
 digitalWrite(ledPin, LOW);
 if(flag == 0){
 Serial.println("LED: off");
 flag = 1;
 }
 }
 else if (state == '1') {
 digitalWrite(ledPin, HIGH);
 if(flag == 0){
 Serial.println("LED: on");
 flag = 1;
 }
 }
}