#include "SoftwareSerial.h"
#define RX    3   // *** D3, Pin 2
#define TX    4   // *** D4, Pin 3
SoftwareSerial mySerial(RX, TX);

const int LED_BLUE = 13;

void setup() 
{
  Serial.begin(9600);
  mySerial.begin(9600);
  pinMode(LED_BLUE,OUTPUT);
  digitalWrite(LED_BLUE,0);
}


void flash()
{
  digitalWrite(LED_BLUE,1); 
  delay(500);
  digitalWrite(LED_BLUE,0); 
}


void loop() 
{ 
  if (Serial.available()>0) 
  {
    mySerial.write(Serial.read());
  }
  if (mySerial.available()>0) 
  {
    Serial.write(mySerial.read());
  }
}