Isn't that precisely the point? There are so many different firewalls and customers loose their passwords, so there has to be a solution that does not invlove changing their firewall.
Since posting the original message, I have found that several of the open source programs have an option for an "inverse connection" . This has the server initiate the connection to the viewer.
Having worked with Radmin for years, I would much prefer to use it in new installations. I like the interface and it works very well. But we need this feature. Do you have it or is there some way to simulate it?