Port Number Reference

How to Use the Port Number Reference

Type a port number or service name into the search field to filter the results instantly. Entering a number like 443 will show the exact port entry for HTTPS. Entering a service name like "Redis" or "PostgreSQL" will match against service names and descriptions. You can also search by category keywords such as "database" or "email" to see all ports in that category. Use the category filter buttons above the table to narrow results to a specific group like Web, Database, or DevOps. Click "Copy Results" to copy the currently visible port entries to your clipboard.

The reference includes over 100 of the most commonly used ports across networking, web development, databases, email, security, and DevOps. Each entry shows the port number, the service name, whether it uses TCP or UDP (or both), the category it belongs to, and a brief description of what the service does.

Understanding Network Ports

A network port is a logical endpoint for communication. Every TCP or UDP connection is identified by a combination of the source IP address, source port, destination IP address, and destination port. This four-part tuple allows a single server to run dozens of services simultaneously. When a web browser connects to a server, it sends data to the server's IP address on port 443 for HTTPS. The server's operating system routes the incoming packet to the web server process that is listening on that port.

Port Ranges and Their Significance

The total port range spans from 0 to 65535. This range is divided into three categories by IANA (Internet Assigned Numbers Authority). Well-known ports (0 to 1023) are reserved for established protocols like HTTP, SSH, and DNS. Binding to these ports on Unix-like systems typically requires root privileges. Registered ports (1024 to 49151) are assigned to specific applications upon request, covering services like MySQL (3306) and PostgreSQL (5432). Dynamic or ephemeral ports (49152 to 65535) are used by client applications for temporary outgoing connections and are assigned by the operating system.

TCP vs. UDP: Choosing the Right Protocol

TCP provides reliable, ordered delivery of data. It establishes a connection through a three-way handshake, retransmits lost packets, and ensures data arrives in sequence. This makes TCP the right choice for web traffic, email, file transfers, and database connections where every byte matters. UDP sends data without establishing a connection and does not guarantee delivery or ordering. This lower overhead makes UDP faster and more suitable for DNS lookups, video streaming, online gaming, and VoIP where occasional packet loss is acceptable and latency is critical.

Security Best Practices for Port Management

Every open port on a server is a potential attack surface. Close all ports that are not actively needed by configuring your firewall to deny incoming connections by default and only allowing specific ports. Use tools like ss -tlnp on Linux or netstat -an on Windows to audit which ports are listening. Move administrative services to non-standard ports when practical, though this is security through obscurity and should not replace proper authentication and encryption. Always use TLS-encrypted versions of protocols when available: HTTPS (443) instead of HTTP (80), IMAPS (993) instead of IMAP (143), and SMTPS (465) instead of SMTP (25).

Frequently Asked Questions

What is a network port number?

A port number is a 16-bit unsigned integer (0 to 65535) that identifies a specific process or service on a networked device. When data arrives at a server, the operating system uses the destination port number to route the traffic to the correct application. Without port numbers, a single IP address could only run one network service at a time.

What is the difference between TCP and UDP?

TCP is connection-oriented, guarantees delivery, and ensures packets arrive in order. UDP is connectionless, does not guarantee delivery or ordering, but has lower overhead. TCP is used for web traffic, email, and file transfers. UDP is used for DNS, streaming, and real-time applications.

What are well-known ports?

Well-known ports range from 0 to 1023 and are assigned by IANA to widely-used protocols like HTTP (80), HTTPS (443), SSH (22), and SMTP (25). On Unix-like systems, binding to these ports typically requires root privileges. Registered ports (1024-49151) are assigned to specific services, and dynamic ports (49152-65535) are used temporarily by client applications.

Why is port 443 important?

Port 443 is the default port for HTTPS, which is HTTP encrypted with TLS. Nearly all modern web traffic uses port 443 because browsers and security standards require TLS encryption. Websites serving content only on port 80 (unencrypted HTTP) are flagged as insecure by browsers.

How do I check which ports are open on my server?

On Linux, use ss -tlnp or netstat -tlnp to list all listening TCP ports. On macOS, use lsof -iTCP -sTCP:LISTEN. On Windows, use netstat -an | findstr LISTENING. For external scanning, tools like nmap can discover which ports are accepting connections.