Port Number Reference

Well-known ports (0–1023) are port numbers assigned by IANA to core internet services. Examples include HTTP (80), HTTPS (443), SSH (22), FTP (21), DNS (53), and SMTP (25). On Unix-like systems, binding to a well-known port typically requires root or administrator privileges.

TCP (Transmission Control Protocol) is a connection-oriented protocol that guarantees reliable, ordered delivery of data. UDP (User Datagram Protocol) is connectionless, providing faster but unreliable delivery without guaranteed ordering. Services like HTTP and SSH use TCP for reliability, while DNS queries and streaming media often use UDP for speed.

Two services cannot listen on the same port and protocol simultaneously on the same IP address. However, a service can use the same port number on different protocols (e.g., DNS uses port 53 on both TCP and UDP). Different IP addresses on the same machine can also have different services on the same port.

Ephemeral (dynamic) ports range from 49152 to 65535. The operating system assigns these temporarily to client applications when they make outbound connections. Once the connection closes, the port is released back to the pool. The exact range varies by OS — Linux often uses 32768–60999.

On Linux/macOS, use ‘netstat -tlnp’ or ‘ss -tlnp’ to list listening TCP ports, or ‘nmap -p PORT HOST’ to scan a remote host. On Windows, use ‘netstat -an | findstr PORT’. You can also use ‘telnet HOST PORT’ or ‘nc -zv HOST PORT’ to test connectivity to a specific port.

Yes. All port data is embedded in the page and processed entirely in your browser. No network requests are made, no search queries are tracked, and nothing is sent to any server. The tool works fully offline once loaded.

Yes. While IANA assigns specific services to specific ports, you can configure any application to listen on any available port. However, avoid using well-known ports (0–1023) for custom services to prevent conflicts with standard services. Registered ports (1024–49151) should also be checked for conflicts. Dynamic ports (49152–65535) are generally safe for custom use.