Port Number Reference
The network ports worth knowing — searchable, with honest warnings.
About this reference
Forty-ish ports with names, jobs in plain language, and — where earned — security warnings. Search by number, protocol or purpose ("database", "mail"). No 65,535-row data dump; just the ones that appear in real error messages and firewall rules.
The system behind the numbers
Ports are how one machine runs many conversations: the IP address finds the computer, the port finds the program. The numbering has structure worth knowing. 0–1023 are the "well-known" ports, historically requiring root to bind — which is why the ancient protocols live there (22 SSH, 25 SMTP, 53 DNS, 80/443 web). 1024–49151 are registered to applications (3306 MySQL, 5432 Postgres, 6379 Redis). Above that, ephemeral — your browser's end of every connection. Dev servers cluster at 3000, 5173, 8000 and 8080 for one reason: memorable numbers safely above the privileged line. The security column matters most: a handful of ports are perennial breach headlines when internet-exposed — RDP 3389 (brute-force magnet), SMB 445 (ransomware's traditional door), Redis 6379 and MongoDB 27017 (historically unauthenticated by default), Elasticsearch 9200. The honest rule they share: databases and remote-desktop belong behind a VPN, never on the open internet. The subnet calculator, URL parser and HTTP status reference are this page's neighbours on the networking shelf.
Frequently asked questions
What's the difference between port 80 and 443?
80 is HTTP (unencrypted), 443 is HTTPS (TLS) — and the modern web is essentially all 443, with 80 surviving mainly to redirect. If a site works only on 80, that's a finding.
Why do dev servers use 3000 and 8080?
Ports below 1024 historically required root to bind, so development tools picked memorable numbers above the line: 3000 (Node/Rails), 8000 (Python), 8080 (HTTP's understudy), 5173 (Vite).
Which ports should never face the internet?
Databases (3306, 5432, 6379, 27017, 9200), Windows file sharing (445) and RDP (3389) top the breach statistics. VPN or SSH-tunnel access; never a naked exposure.
Is this every port?
No — 65,535 exist and most mean nothing in particular. This is the working set: the ports in error messages, firewall rules, scan results and tutorials.