A port is like a numbered doorway that routes traffic to a specific service running on a server. The IP address gets you to the right device; the port number gets you to the right application on it.
The most common ports
- 20/21 — FTP: file transfer protocol.
- 22 — SSH: secure remote access to servers.
- 25 — SMTP: sending email.
- 53 — DNS: domain name resolution.
- 80 — HTTP: unencrypted web traffic.
- 110 — POP3 / 143 — IMAP: email retrieval protocols.
- 443 — HTTPS: encrypted web traffic — the modern standard.
- 3306 — MySQL: database connections.
- 3389 — RDP: Windows remote desktop.
- 8080 — HTTP-alt: commonly used in dev environments or proxies.
When is an open port a risk?
An open port alone isn't a vulnerability — but unnecessarily exposed management ports (like 3389 or 22) are a top target for attackers. Use our port check tool to quickly see what's exposed on a host.
A practical tip
Keep management ports behind a VPN where possible, enforce strong authentication, and shut down services you're not using.