Quiz: what a server exposes

Read the output

Part of a server inventory. Which program here is not visible to an outside machine?

$ sudo ss -tlnp
Local Address:Port   Process
0.0.0.0:8080         users:(("python3",pid=1046,fd=3))
127.0.0.53%lo:53     users:(("systemd-resolve",pid=437,fd=15))
0.0.0.0:22           users:(("sshd",pid=773,fd=3))
[::]:5432            users:(("postgres",pid=1210,fd=7))

• A python3 — its port 8080 is not a standard one.
• B postgres — it has an IPv6 address.
• C systemd-resolve — it listens on 127.0.0.53.