Server Database with txt doc

I know you can get data from websites and stuff. But is there a way I can have text document that only I can update with data that can be updated in game? So for example if somebody made an account on my website and I got the information for the account. Then I added the information to a text file and that file updates over the server so that people can use there login information and sign into the game. Would I need a website for this or could I just use something within unity?

Also I want...

Server Database with txt doc