How do you tie the license to machine locked and an e-Commerce system?

[saf-itpro]

I don’t see a role of any database (SQL Server , SQLite etc.). How do we achieve the following:

1. User pays at PayPal. PayPal sends an email to our server with payment ok status
2. Our server sends an email to client asking for their machine ID and sends a machined locked license to the client’s email
3. Client copies the license to the software and clicks on an activate button. The button verifies the license at the server and sends an ok status. The software gets activated
   Thanks..Saf