Non standard mysql port

I am attempting to use Drupal on a cluster where the mysql services runs on a non standard port. How do I tell drupal which port to use? I have tried a number of iterations with the $db_url variable but none have worked out so far... For instance the following does not work...

$db_url = "mysql://user:password@mymachine.mylocation.edu:port/DrupalSite";

Thanks