Port Numbers Reference

What is Port Numbers Reference?

The Port Numbers Reference tool provides instant lookup of TCP and UDP port numbers used by common network services and protocols. Whether you’re configuring a firewall, troubleshooting network issues, or studying cybersecurity, this reference helps you quickly identify what each port is used for and understand associated security considerations.

Port numbers are divided into three ranges: Well-Known Ports (0-1023) reserved for standard services, Registered Ports (1024-49151) for user applications, and Dynamic/Private Ports (49152-65535) for temporary connections.

How to Use

1. Search by Port Number: Enter a port number (e.g., 80, 443, 3306) to find the associated service and protocol.
2. Search by Service Name: Enter a service name (e.g., HTTP, SSH, MySQL) to find its default port.
3. Filter Results: Use category and protocol filters to narrow down results by port range (Well-Known or Registered) or protocol type (TCP, UDP, or both).
4. View Details: Each result shows the port number, protocol(s), service name, description, and security notes.
5. Copy to Clipboard: Click the copy button on any result to copy the port information to your clipboard.

Common Use Cases

• Firewall Configuration: Quickly identify which ports need to be opened for specific services.
• Network Troubleshooting: Understand what service is using a specific port when diagnosing connectivity issues.
• Security Auditing: Review open ports on your system and understand associated security risks.
• Application Development: Choose appropriate ports for custom applications while avoiding conflicts.
• System Administration: Document and manage services running on your network infrastructure.
• Cybersecurity Studies: Learn about common attack vectors and ports targeted by malicious actors.

Frequently Asked Questions

What is a port number?

A port number is a 16-bit unsigned integer (0-65535) that identifies a specific process or service on a computer. Combined with an IP address, it creates a unique communication endpoint. Port numbers allow multiple services to run on the same machine and enable proper routing of network traffic.

What’s the difference between TCP and UDP ports?

TCP (Transmission Control Protocol) is connection-oriented and guarantees reliable, ordered delivery of data. It’s used by services like HTTP, HTTPS, SSH, and FTP. UDP (User Datagram Protocol) is connectionless and focuses on speed over reliability. It’s used by DNS, DHCP, streaming, and online gaming. Some services support both protocols on the same port.

Why are Well-Known Ports (0-1023) restricted?

Well-Known Ports are reserved for standard, widely-used services established by IANA (Internet Assigned Numbers Authority). On most operating systems, only administrators or root users can bind services to these ports, preventing unauthorized services from impersonating standard services and improving security. This protects users from malicious applications claiming to provide standard services.

Can I use any port for my application?

You can use any port in the Registered (1024-49151) or Dynamic (49152-65535) ranges on your own system without administrator privileges. However, avoid well-known ports to prevent conflicts with standard services. Always check common port registrations to avoid conflicts with other applications, and consider security implications when choosing publicly-accessible ports.

Is opening port 22 (SSH) dangerous?

SSH itself is secure with strong encryption, but exposing port 22 to the internet makes it a target for brute-force attacks. Best practices include: use key-based authentication instead of passwords, run SSH on a non-standard port, restrict access via firewall rules, disable root login, and keep your system patched. When properly configured, SSH is one of the safest remote access methods.

How do I check what services are using specific ports on my system?

On Linux/Mac, use lsof -i :PORT or netstat -tulpn | grep PORT. On Windows, use netstat -ano | findstr :PORT or Get-NetTCPConnection | Where-Object LocalPort -eq PORT in PowerShell. These commands help identify running services and their associated processes.

Security Considerations

• Always run ports requiring elevated privileges (0-1023) only for legitimate services
• Close or restrict unnecessary ports with firewall rules
• Use non-standard ports for exposed services when possible (security through obscurity is not full security, but a helpful layer)
• Implement strong authentication and encryption for remote access services
• Regularly audit open ports on your systems
• Keep services updated to patch security vulnerabilities
• Monitor port activity for suspicious or unexpected connections