Reference

TCP/UDP Port Reference

Common TCP and UDP ports and the services that use them — with transport, purpose and security notes for each. Click any port for the full page.

Why ports matter

Ports let one host run many services at once — a web server on 443, SSH on 22, DNS on 53. Firewalls and ACLs allow or block traffic by port, which is why knowing them is core to networking and security. Learn firewall filtering in the CyberOps course.

Frequently asked questions

What is a network port?

A port is a 16-bit number (0–65535) that identifies a specific service on a host, so multiple services can share one IP address. HTTPS uses 443, SSH uses 22, DNS uses 53.

What is the difference between TCP and UDP ports?

TCP ports are for connection-oriented, reliable delivery (web, email); UDP ports are for connectionless, low-latency traffic (DNS queries, VoIP, DHCP). Some services use both.

Which ports are the most security-sensitive?

RDP (3389), SMB (445), Telnet (23), and database ports like 3306 and 1433 should never be exposed to the internet — they are common breach vectors.

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