#include <SoftwareSerial.h>  // call library for Serial transfer

int blueTx = 2;  // Tx (set pin for transfer)
int blueRx = 3;  // Rx (set pin for receiver)
SoftwareSerial mySerial(blueTx, blueRx);  // define structure for Serial transfer

int abc=0;

void setup() {
  // put your setup code here, to run once:

    Serial.begin(9600);  // Serial monitor
    mySerial.begin(9600);  // Bluetooth Serial
    
}

void loop() {
  // put your main code here, to run repeatedly:
    abc = abc++;
    
    if ( mySerial.available() ) {
        Serial.write(mySerial.read());  //  put to Serial monitor about Bluetooth contents
    } else { Serial.print(abc); Serial.println(" : Bluetooth serial is not available"); delay(3000);}

    if ( Serial.available() ) {
        mySerial.write(Serial.read());  // write to Bluetooth about Serial monitor contents
    } else { Serial.print(abc); Serial.println(" : Serial is not available"); delay(3000);}
}