Quiz: what a server exposes

Read the output

A check from the outside machine. What makes the 5432 answer different from the 8080 one?

$ sudo ip netns exec lab-outside nc -zv -w 2 192.0.2.1 5432
nc: connect to 192.0.2.1 port 5432 (tcp) failed: Connection refused
$ sudo ip netns exec lab-outside nc -zv -w 2 192.0.2.1 8080
nc: connect to 192.0.2.1 port 8080 (tcp) timed out: Operation now in progress

• A Nobody listens on 5432 at the network address, and the filter silently drops the packets to 8080.
• B 5432 is closed by the filter, and 8080 is held by a hung program.
• C There is no difference — both ports are closed, nc just waited differently.