Glossary / Networking & connectivity

Port (network port)

A port is a numbered door on a machine that lets one server offer many services on one IP address: web traffic knocks on 443 (HTTPS), email on other well-known numbers, databases on theirs. Firewalls work largely by deciding which doors are open to whom. "Close every port you don't need" is the oldest hardening rule there is, and still one of the best.