Let's say we have a wifi at home. When I google "whatsmyip", it gives me public IP address, which is essentially IP address of my router on the internet.
Now lets say I have two machines (A and B) both hosting a web server. I want to reach to a web-server on my machine 'A' from outside my local network (from some other corner of the world), how I can ping to that specific machine to my network. I understand for outgoing requests from my machine we have NAT, but what about incoming request to a specific machine? How router resolves it?
How I can check that IP(for incoming requests) in my windows/linux machine?
e.g let's say I have a tomcat server running on port 8080 on machine A. Now if I do localhost:8080/home, it displays "Hello World". Now one of my friend in let's say in Europe wants to access "/home" end point. What ip would he use?{IP}:8080/home. Means how he'll identify my machine, as to the internet only router's IP address is visible
To be able to reach your comptuer on the LAN behind your router you will need to do a port forward.
All connections to your public x.x.x.x:p ip/port address are forward to y.y.y.y:p
You can't forward different connections with the same port to a different machine in your lan, you will have to implement a more sophisticated approach to be able to do that, like a load balancer and apply a rule's base on the domain etc.
To be able to ping, you have to forward ICMP request to your lan machine.