I'm not sure if I remember that right, but I managed to do this by changing the VM's networking settings in VirtualBox without port-forwarding but rather by changing the first adapter's type to bridged networking (with port-forwarding I also had the problem that the site didn't display anything in esv-private).
Note that you then probably need to call the frontend on your host by using http://your-guest's-local-IP:9001/#/esv-private. Also it should be necessary to change some config files so that the servers actually serve requests from anywhere else then the localhost.
That worked for me, but I still had/have some problems when running some experiments which are instantly raising some kind of exception after starting the simulation, but that's a story for its own thread.
If there are better ways on doing this, I would be interested in them as well!