The default port for RAdmin is 4899. 127.0.0.1 is sort of not precise. You actually don't want to monitor localhost, but your address on the network.

Easy ways include: 1) to have a script that runs netstat periodically: netstat -a 10 etc. You can do it through open2, so your script can alert you when centain port is connected. 2) run firewall on your PC (some company does not allow employee to run firewall on their PC, you have to check this first)

A more complex (might be better) way is to do some pcap programing. But this might be over-engneered, as most likely netstat should be good enough in your case.