This is a super simple working demo implementation with only one relay connection allowed, without NAT traversal, persistence, encryption and any other advanced features. But it can be your good starting point to write your own RustDesk server program.
# install rustup first, https://rustup.rs/
IP=<public ip of this machine> cargo run
https://rustdesk.com/blog/id-relay-set/
If you still need my private help, buy me a good hotpot please!