If you intend to connect to a computer residing on a corporate, academic, or other network not under your personal control, you may experience issues with Screens, Screens Connect, and Screens Express. These types of "semi-public" networks are often configured more securely than home networks, and don't necessarily need to offer consumer-friendly network services such as UPnP (Universal Plug-and-Play) and NAT-PMP (Network Address Translation-Port Mapping Protocol).
Screens Connect and Screens Express require the availability of one of these protocols in order to automatically forward a public network port from the router to the private network port on the computer you wish to connect to. Without Screens Connect or Screens Express, port forwarding must be configured manually on the router. Without a forwarded port, Screens will be unable to communicate with the computer, so if you don't have administrative access to the router, you must ask for assistance from the network administrator.