First of all, I know this question has been asked before
It seems, however, that none of these yet have a full solution. My question is essentially the same. I have a device connected to a wifi network, am also setting up a server on port 8080, but due to the way NAT routers work, there is no way to send requests to the individual device as it shares a public IP with numerous other computers.
The accepted answer mentioned a multitude of workarounds, but it seems that such necessary functionality needs to exist in some legitimate form. (Note video games for example. Even clients still need to be sent packets, and I have yet to see my games do any port forwarding on my router on their own.)
In fact, pretty much any application that interacts with the internet needs to receive data and requests from the internet without forwarding ports. How is this done?
Best Answer
Connection tracking.
If the device connects from inside the NAT to outside, then related packets from the outside system are permitted in. This can be done with both TCP and UDP in some cases.