int recv = 0;

// 0 FORWARD
// 1 BACKWARD
// 2 LEFT
// 3 RIGHT

void setup() {
  Serial.begin(115200);  //initial the Serial
}

void loop() {
  
  if (Serial.available())  {

      switch (Serial.read())
      {
        case 0:
          Serial.println("MOVING FORWARD");
          break;

        case 1:
          Serial.println("MOVING BACKWARD");
          break;

        case 2:
          Serial.println("MOVING LEFT");
          break;
        case 3:
          Serial.println("MOVING RIGHT");
          break;
        default:
          Serial.println("INVALID INSTRUCTION");
      }

  }
}