expresso is a command-line interface to control the ExpressVPN app. It uses the same native messaging interface as the open-source ExpressVPN browser extension.
The expresso package is installed locally on your computer. When you connect to a VPN, the ExpressVPN app will start an expresso agent in the background. The agent relays virtual network interface events back to expresso which then forwards them along with any commands you enter into the command-line interface.
$ sudo port install expresso
# Connect $ expresso connect US # Change current location when already connected $ expresso connect --change US # Choose a random location in the given country $ expresso connect --random # Disconnect $ expresso disconnect
More info: https://github.com/sttz/expresso