#include<SoftwareSerial.h>// add serial library
int rxPin = 1;// the receiver will be in pin 1
int txPin = 0;// the sender will be in pin 0
char val = 'a';// defining that val is equal to 1

SoftwareSerial myserial(rxPin, txPin);// defin the serial and indecate the ports.

void setup() {
  myserial.begin(9600);
  pinMode(7, OUTPUT);// pin 7 is the LED
 }

void loop()
{
  char chr = myserial.read();// chr equal whatever the serial read from the master
   if (chr == val) {// here I'm saying if the serial read a valuy equal to what val is, turn LED ON and send that it receive
  for (int x = 0; x < 1; x++) {
   digitalWrite(7, HIGH);   // set the LED on
   delay(500);              // wait for a second
   digitalWrite(7, LOW);    // set the LED off
   delay(500);              // wa
    }
  }
 }