In checking hits to my router I am seeing someone trying to get to my network using port 4899 which is your registered port. Does this mean that the individual is looking to see if that port is open for hacking purposes? My router is set to deny and of course doesn't answer pings. I may propose your product as a replacement for PCAnywhere. I do not fully understand the issue of having any additional port open for hackers. How can I answer this question to the user?
Someone could ping port 4899. I would not be surprised if there are 'bots' floating around scanning port 4899 on remote machines to see if there's a radmin service running. Make sure you have an excellent secured password.
NOTE: Even PC Anywhere has 'additional ports' open. To remotely access a computer, some connection must be made over a port.
If someone has a radmin client and tries to connect to an IP address, it will try on port 4899 (as you're describing above). In all likeliehood, someone is just trying to connect using the radmin client. If you see a zillion requests on port 4899, that's a different story. But just one...maybe two...and it's probably not a hacker.
There's no more security issues here than in ANY other remote-control program. Radmin is secure and version 2.2 is even better than the previous!