Searchable reference of common TCP and UDP port numbers used in networking, security, and system administration. Filter by protocol type, search by port number or service name, and see which services use each port along with security considerations. Covers well-known ports (0-1023), registered ports (1024-49151), and commonly encountered services. Designed for network engineers, firewall administrators, and security professionals who need a quick, no-nonsense port lookup.
| Port | Protocol | Service | Description / Notes |
|---|
netstat -tlnp (Linux) or netstat -an (Windows) to view listening ports.
Use nmap -sV target to scan and identify services.
Well-known ports are TCP and UDP port numbers in the range 0-1023, assigned by IANA to common services. Examples include port 80 (HTTP), 443 (HTTPS), 22 (SSH), 53 (DNS), and 25 (SMTP). On most operating systems, binding to a well-known port requires elevated privileges (root or administrator). These ports are the primary targets in network security scanning.
TCP (Transmission Control Protocol) is connection-oriented — it establishes a session, guarantees delivery order, and retransmits lost packets. UDP (User Datagram Protocol) is connectionless — it sends packets without establishing a session, with no delivery guarantee. TCP is used for reliable transfers (HTTP, SSH, email), while UDP is used for speed-sensitive applications (DNS queries, VoIP, video streaming, gaming).
Ephemeral ports (also called dynamic or private ports) are temporary port numbers in the range 49152-65535 that the operating system assigns to client-side connections. When your browser connects to a web server on port 443, your OS picks a random ephemeral port (e.g., 52847) as the source port. These ports are automatically released when the connection closes. Firewalls typically allow outbound traffic from ephemeral ports.