On the server's page you should be able to start the server up with a password chosen by the owner of the server. This should be disabled by default (for privacy/security reasons), but available for those who want it. On the page, there should be ads and a captcha (google's recaptcha prefferably) because bots could exploit this... Passwords should not be unsecure for the bot reasons.
Players should be only able to start the server, nothing else...