mailer software upgrade

i have a software written in visual studio 2005 c ++ and need to have a small modification done to it, i need it to have an activation method to activate on my server, via ftp or http, we can use a unique key code for each client to do this? i have the source codes from my last coder. ## Deliverables what i need is the application to do an activation method to connect to my server with? using unique key codes. we could use mysql or upload .txt files to my server using ftp. the software will then check to see if the unique key codes are present on the server if so it will say "activated" if unique key code is not present on the server software will say "not activated"