Please add support for rfc6613 and rfc6614

[rgutierrez2004]

Please add support for
rfc6613 - RADIUS over TCP
rfc6614 - Transport Layer Security (TLS) Encryption for RADIUS

[JonasKs]

I'm interested in this as well, @moznion. Would you accept a PR if I give it a shot? I assume we can do this with tokio-OpenSSL and by modifying the Server implementation?

Also just read this article from Cloudflare, which was really good.

[JonasKs]

A better solution for me would be RFC7360, which is UDP DTLS. Some Cisco devices don't seem to support RFC6614, unfortunately.
There's an implementation for a UDP-DTLS server here.