How do my servers know each month when a recurring payment is successful?

Is Directpost Configuration how I let my servers know each month when a recurring payment is successful?  Is it as simple as that.  I am using a c# wpf program to subscribe to a recurring payment for my customers and I understand how to easily read the message and response code in the receipt.  I am just not sure how to update my servers on a monthly basis?  Any help would be greatly appreciated.

Thank you,

Paul