To be more clear, the Nat Punchthrough stuff is NOT implemented in EOS OSS plugin right now.
It IS implemented in the EOS SDK but it is not implemented in the plugin for EOS you can get for free in the plugin list.
So your options are to manually utilize the EOS SDK stuff or to use 3rd party $130 EOS plugin from redpoint (haven’t tried it myself but they claim it works):
You could also just use the steam subsystem instead which based on others post DOES have NAT punchthrough stuff built in. However, that requires a steam app ID which costs $100. However that app id also lets you publish to steam.
I wasted a ton of time thinking the EOS plugin has NAT stuff built in hope I can save people some time by being more explicit.