I needed to maintain a continuous (or near-continuous) VPN connection to a server (server 1) from another server (server 2) that was running a Tomcat web-app (on Ubuntu Server 16.04). Server 1 was part of a network which provides secured VPN access to external connections via Cisco Anyconnect.
Users have reported that this approach does not work with newer version of openconnect etc.
Given I haven't attempted this approach (nor have need of it) I am just leaving this here for historical purposes (or something that did work previously).
For this, we're going to use the excellent OpenConnect to connect to server 1, and a bash script to continuously check the connection, and if disconnected, to reconnect.