UPnP

This simple plugin allows your server to automatically open network ports on supported routers using UPnP. It will automatically open the server port, and you can define additional ports in the config.yml file. You can also chose whether to automatically close the ports when your server stops.

UPnP is intended to be as lightweight and simple as possible, and only has four dependencies, used for logging, access to the spigot api, and bstats. Overall, UPnP is written in 896 lines of code.