In this article
What Are Network Ports?
Network ports are logical endpoints for communication in TCP/IP networking. Each port is identified by a 16-bit number (0-65535) and associated with a specific protocol or service. Ports allow a single IP address to host multiple services simultaneously — HTTP on port 80, HTTPS on 443, SSH on 22, and so on.
The Internet Assigned Numbers Authority (IANA) maintains the official registry of port assignments. Knowing which ports common services use is essential for server administration, firewall configuration, and network security auditing.
How Ports Work
Ports are divided into three ranges defined by IANA, each serving a different purpose in network communication.
- Well-known ports (0-1023) — reserved for standard services like HTTP (80), HTTPS (443), FTP (21), SSH (22), DNS (53), and SMTP (25)
- Registered ports (1024-49151) — assigned to specific applications like MySQL (3306), PostgreSQL (5432), Redis (6379), and MongoDB (27017)
- Dynamic ports (49152-65535) — ephemeral ports assigned temporarily by the OS for client-side connections in outbound requests
Try it free — no signup required
Browse Port Reference →When To Use a Port Reference
A port reference is essential for anyone managing servers, configuring firewalls, or troubleshooting network issues.
- Firewall configuration — know exactly which ports to open for each service and which to block to minimize the attack surface
- Server setup — verify the default port for services you deploy and check for conflicts with existing services on the same host
- Security auditing — identify unexpected open ports that could indicate unauthorized services or potential vulnerabilities
Frequently Asked Questions
What is the difference between TCP and UDP ports?
TCP ports provide reliable, ordered, connection-based communication — ideal for web traffic, email, and file transfers. UDP ports provide faster, connectionless communication — used for DNS queries, video streaming, VoIP, and gaming where speed matters more than guaranteed delivery.
Can two services use the same port?
Not simultaneously on the same protocol and IP address. Each combination of IP address, protocol (TCP/UDP), and port number must be unique. However, a TCP service and a UDP service can both use port 53 (as DNS does) because they are different protocols.
Why are some ports considered dangerous to leave open?
Ports running services with known vulnerabilities become attack vectors. Commonly targeted ports include 23 (Telnet, unencrypted), 445 (SMB, ransomware vector), 3389 (RDP, brute force target), and 1433 (MSSQL). Always close unused ports and keep services on open ports updated.