§ 01
Definition
Many companies run Cisco, Palo Alto GlobalProtect, Juniper/Pulse or Fortinet VPN gateways. OpenConnect lets Linux, macOS and other users connect to many of these without the vendor's own client, and ocserv offers a free server that speaks the same protocol.
§ 02
How it works
The client authenticates over HTTPS, then carries traffic through a TLS tunnel, with an optional DTLS (UDP) channel for better speed. Because it runs on port 443 and looks like web traffic, it is also popular in places where VPNs are filtered.
§ 03
Why it matters
OpenConnect matters mostly for remote workers and system administrators. It shows that 'SSL VPN' is still widely used in business, even as consumer apps move to WireGuard.