UPNP Plugin is code plugin to make you easy to add and delete UDP/TCP port mapping on network devices which are compatible with UPNP Protocal (https://en.wikipedia.org/wiki/Universal_Plug_and_Play). It allows your game to use P2P under NAT. It's based on WANIPConnection:1 Service Template Version 1.01 (http://upnp.org/specs/gw/UPnP-gw-WANIPConnection-v1-Service.pdf). It uses SocketSubsystem and HttpModule in UE4 and exposes necessary fuctions in blueprint. It doens't use any third party library.