Running Windows 10 host with Ubuntu 17.04 guest in VirtualBox. VirtualBox host-only adapter established. I can ping guest (192.168.56.101) from host and ping host (192.168.56.1) from guest. Set up small NGINX demo as proxy listening on port 80 to spawn-fcgi on port 8000 to small C++ app. App responds to browser in guest requesting "localhost", but connection from browser on host is refused. ufw status is Inactive. Any ideas will be appreciated.