Backand Developer for a simple IP and Unique code development for a Unity project

Hello, I'm making an app and I need a server where I can store Device Unique Identifier number and codes which can be used to login. I need someone to produce those codes and check from the server side if the code I type is valid and if so send me back info so I can login or not. I have Heroku account and a server but it's down at the moment. Would be great if we can use Heroku server for this cause part of this project was working there before it went down.