net/sslh 2.3.1 FreeBSD

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.