net/sslh just came to my attention:
"sslh accepts connections on specified ports, and forwards them further based on tests performed on the first data packet sent by the remote client."
That sounds useful.
FreshPorts -- net/sslh: SSL/SSH multiplexer
sslh accepts connections on specified ports, and forwards them further based on tests performed on the first data packet sent by the remote client. Probes for HTTP, TLS/SSL (including SNI and ALPN), SSH, OpenVPN, tinc, XMPP, SOCKS5, are implemented, and any other protocol that can be tested using a regular expression, can be recognised. A typical use case is to allow serving several services on port 443 (e.g. to connect to SSH from inside a corporate firewall, which almost never block port 443) while still serving HTTPS on that port. Hence sslh acts as a protocol demultiplexer, or a switchboard. With the SNI and ALPN probe, it makes a good front-end to a virtual host farm hosted behind a single IP address. sslh has the bells and whistles expected from a mature daemon: privilege and capabilities dropping, inetd support, systemd support, transparent proxying, chroot, logging, IPv4 and IPv6, TCP and UDP, a fork-based and a select-based model, and more.
(www.freshports.org)