mod for authentication of users

I am having some registered users on my forum. I want to allow only registered users to connect to my server. For this I need the player authentication against MYSQL Db. Not sure if there is any mod available for it.

Any help is welcome.

It's not nearly as sophisticated or pretty as what you're asking for, but the easy solution would to just password protect the server and send the password out in the registration email.

That is a gud input. But let me explain my requirement ...

The registered user enters into the site and creates a match with some other user. Both get notified about the match... and the match data is maintained in the MYSQL DB.

I have an application which continuously queries the DB for upcoming matches and if it finds a match scheduled for current time then it should only allow the two players between which the match is scheduled the play the match.

However if I only password protect the server then at any time any one apart from the users between whom match is supposed to happen can also login... how can I solve this?

That's way over my head. Sorry.