In Port Address Translation, PC with Private IP address sends a packet with Destination address as a public IP address to the router. The router changes the Source address to the public router address and assigns a random port number for response. When packet reaches the destination, it should see return address and port. The destination sends a packet with routers public ip and same port. The router then remaps the packet to internal ip using the port number information. The port then stops listening after a timeout.
Websites like Whatismyip show only the routers public ip and not the port. How can I find the port number?
If the port number is found, can I use this as a temporary Port Forwarding? For example, send a packet to router public ip:port to connect to the computer. Or will the router ignore it because the source address was different compared to the destination address of the packet sent.