Ports
Ports number the different services on one server, so one IP can run many services at once.
Think of it like this
The IP is a building's address; the port is the room number. A delivery needs both.
In this setup
Ports used by this setup: 22 SSH, 80 certificate validation, 443 main node, 2443 backup node, 2096 subscription, 8318 CLIProxyAPI, 53998 3x-ui panel. The firewall only allows these; everything else is closed.
Common misconceptions
- "Opening more ports is more convenient": every open port is another door to scan and attack. Close what you do not use.
- "Moving SSH off port 22 makes it secure": it stops some automated scans, but real security comes from key-only login.
Related: Firewall, SSH, public and private keys, IP address