If you are using RustDesk you should have your own RustDesk Server, these docs will help you on your RustDesk journey.
Ports required for RustDesk Server self-hosting depends largely on your environment and what you want to do with RustDesk. The Examples shown throughout the docs will have generally have all ports suggested to be opened.
The above are the minimum required ports for RustDesk to work, these handle the signal and relay ports as well as NAT traversal.
Additionally TCP ports
21119 can be opened if you want to use the RustDesk Web Client.
For Pro users without an SSL Proxy you will need to open TCP port
21114 for the API to work alternatively using an SSL Proxy open TCP port
To check ports are opened and working you can use
test-netconnection domain.com -p 21115 with PowerShell or CanYouSeeMe.org.