Remote Authentication

I have a desktop software (maked in powerbuilder, like a delphi software) that calls my drupal website, and in this software i need that the user could be authenticated to be able to navigate around the site, post forum topics, post comments ... Does exist a way i can obtain this? Im trying to do this with CURL, but i not obtain any sucess. (i see this article http://drupal.org/node/80548).