The openconnect package summarizes itself as the "Open client for Cisco AnyConnect VPN".
Here is a youtube video showing an openconnect session being started from the command line:
I tried creating a connection via the NetworkManager software but it exited without giving me good feedback.
When running openconnect (as root) via the command line I got an error:
VPN service unavailable; reason: No address available for SVC connection.
Creating SSL connection failed
Apparently this means I am missing an IP Address pool as discussed under the heading "Check the IP Pool in WebVPN Profile" here
A Linux option for SSL VPN is openvpn-als http://sourceforge.net/projects/openvpn-als/
That looks like a server-side configuration error, and not openconnect's fault. Does this server work with *any* clients, with no IP Address pool configured?
The fact that NetworkManager doesn't give you a coherent response is a PITA; please file a bug in bugzilla.gnome.org (and/or with your Linux distribution) for that.
Yes David you are correct, I hadn't set up the IP Address pool on the ASA to allow connection. Once I did openconnect happily grabs an IP Address and connects.