How do two computers connect to same external address through NAT?

Question

If I have two internal computers connecting to the same external IP address through a NAT router, how is the router able to get the traffic to the correct internal computer?

Answer 1

Since public facing or external IP Address that was given by Internet Service Provider (ISP) has been discussed, I would like to add on this. You can ask your ISP to have your public IP Address not change. It will become static, so that you do not have to inform your friends to change the IP Address if they want to access your server inside your Network Address Translator (NAT). As of this writing, static IP Address cost around 100 bucks. Most of the ISP they call it business account. You can determine your public facing IP Address by googling "what is my ip address".