Port Reference

What It Does

A searchable quick-reference for over 40 common network port numbers. Filter by port number or service name to instantly find the protocol, transport (TCP/UDP), and a brief description. Useful during debugging, firewall configuration, Docker port mapping, and security audits.

Essential Ports at a Glance

• 21 FTP · 22 SSH · 25 SMTP · 53 DNS
• 80 HTTP · 443 HTTPS · 8080 HTTP alt · 8443 HTTPS alt
• 3306 MySQL · 5432 PostgreSQL · 27017 MongoDB
• 6379 Redis · 5672 RabbitMQ · 9092 Kafka
• 2181 ZooKeeper · 9200 Elasticsearch · 5601 Kibana

Port Ranges

• 0–1023 — Well-known ports (IANA assigned, requires root to bind)
• 1024–49151 — Registered ports (application services)
• 49152–65535 — Ephemeral / dynamic ports (OS-assigned for outbound connections)

Useful Commands

• Check open ports: ss -tlnp (Linux) / netstat -an (macOS/Windows)
• What's on port 3000: lsof -i :3000
• Test connectivity: nc -zv hostname 443
• Firewall rule check: iptables -L -n or ufw status

Frequently Asked Questions

What are well-known ports and who assigns them?

Well-known ports are port numbers 0–1023 assigned by the Internet Assigned Numbers Authority (IANA). They are reserved for standard services like HTTP (80), HTTPS (443), SSH (22), FTP (21), and SMTP (25). On Unix systems, binding to ports below 1024 typically requires root/administrator privileges.

What is the difference between TCP and UDP ports?

TCP (Transmission Control Protocol) ports provide reliable, ordered, connection-oriented communication with error checking — used by HTTP, SSH, FTP, and databases. UDP (User Datagram Protocol) ports are connectionless and faster but without delivery guarantees — used by DNS (53), DHCP (67/68), and real-time media streaming.

What ports do common databases use by default?

MySQL/MariaDB uses port 3306, PostgreSQL uses 5432, MongoDB uses 27017, Redis uses 6379, Microsoft SQL Server uses 1433, and Oracle Database uses 1521. These are defaults — production deployments often change them for security reasons.

How do I check which ports are in use on my machine?

On Linux/macOS run ss -tlnp or netstat -tlnp to list listening TCP ports with the process name. On Windows use netstat -ano or Get-NetTCPConnection in PowerShell. lsof -i :PORT shows which process is using a specific port number.

What are registered ports and ephemeral ports?

Registered ports (1024–49151) are assigned by IANA to specific applications (e.g. 8080 for HTTP alternate, 8443 for HTTPS alternate). Ephemeral ports (49152–65535) are dynamically assigned by the OS to the client side of outbound connections and are released after the connection closes.