Abstract: An internal gateway establishes persistent connections to an external gateway through permitted ports and protocols of a firewall. Software on the external gateway and the internal gateway collaborate in order to make available internal, firewall-protected resources to external clients securely and without having to modify network or firewall configurations. Any computing resource such as a web service, web application, or any other network addressable resource residing behind a firewall can be securely exposed in a generic fashion to clients on the external network. No special software is required by clients.