45+ ports every network & security learner should know — searchable, with security notes
Type a port number, service or keyword — or filter by category. Knowing which ports should be open (and which should never be) is a core defensive skill: every open port is a door, and defenders keep an inventory of their doors.
| Port | Service | Protocol | What it does & security note |
|---|
ss -tuln on Linux) and compare against this table. Anything you don't recognize or need should be closed or firewalled.