Project using Ultrasonic Sensor: HC SR04

I have started doing simple project using a ultrasonic sensor and the Bolt Wifi module. I am having a trouble to code it in python, can someone help me with it?
This was my code:!
The output I got was always 0.
need help

You will have to use Arduino for the same because bolt cannot directly interface with this sensor.
Connection of Bolt to Arduino will be like
Write a simple echo program in Arduino editor and by serialRead write a simple program in cloud/VMware.