OpenVPN is an easy-to-use, robust, highly configurable, cross-platform
VPN (Virtual Private Network) daemon which can be used to securely link
two or more private networks using an encrypted tunnel over the internet.

It can forward a tun(4) interface over a single UDP or TCP port with
support for NAT, dynamic endpoints, compression, fragmentation and keep-
alive. It uses OpenSSL's encryption, authentication, and certification
features, with static keys, certificates or TLS-based key exchange.