Carrier Service APP / prepare_shipment

[nthSifiso]

I just created a carrier service and it works just fine. I was wondering what when the customer completes the checkout with the courier rate they got from my app. In other terms, how do I go about creating a callback that waits for Shopify to notify the app after the customer completes the checkout with the courier I provided?

Thank You

[nthSifiso]

I got the answer. Shopify is going to make two requests to the carrier service that you made. 

1. Request for shipping rates: This request is sent by Shopify to your carrier service when a customer is checking out and has selected your carrier service as the shipping option.
2. Request to prepare shipment: This request is sent by Shopify to your carrier service after a customer has placed an order and you have received a request for shipping rates.

To add the separate callback_urls for the two steps above for the code below when you are creating your Carrier services

Thank you