FreeBSD: How to set up an UPnP Internet Gateway Device (IGD) with MiniUPnP and FreeBSD 9.0

Universal Plug and Play (UPnP) is a set of networking protocols that permits networked devices, such as personal computers, printers, Internet gateways, Wi-Fi access points and mobile devices to seamlessly discover each other's presence on the network and establish functional network services for data sharing, communications, and entertainment.

The MiniUPnP project offers software which supports the UPnP Internet Gateway Device (IGD) specifications.

For the purposes of this article I'll assume you're familiar with setting up NAT under FreeBSD using OpenBSD Packet Filter. I'll also assume that your machine is up, routing and translating traffic correctly and is protected by OpenBSD Packet Filter (PF).