#include <SoftwareSerial.h>

const int RX=-1;
const int TX=2;

SoftwareSerial mySerial(RX, TX);
#define TRIG_PIN 3
#define ECHO_PIN 4

// defines variables
long duration;
int distance;

void setup()
{
pinMode(TRIG_PIN, OUTPUT); // Sets the trigPin as an Output
pinMode(ECHO_PIN, INPUT);

mySerial.begin(9600);
mySerial.println("Hello, world?");
} 
  
void loop() {
  // Clears the trigPin
digitalWrite(TRIG_PIN, LOW);
delayMicroseconds(2);
// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(TRIG_PIN, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG_PIN, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(ECHO_PIN, HIGH);
// Calculating the distance
distance= duration*0.034/2;
// Prints the distance on the Serial Monitor
mySerial.print("Distance: ");
mySerial.println(distance);
}