Very but as with the example he is giving, this is very useful technology for video games where hosts and clients are regularly behind NAT. UPNP has made this s

Very but as with the example he is giving, this is very useful technology for video games where hosts and clients are regularly behind NAT. UPNP has made this somewhat better but it's still no where near perfect. If i'm not mistaken, much of the UDP punch-through technology was invented by Skype. However, skype still relies on a proxy server that every client connects to. It needs that so that the client can prepare the router to let data through from a certain client IP. These guys here found a ridiculously clever way of skipping this step which makes true P2P with both end points behind NAT possible and even easy to implement.