Port Scanner Simulator
A searchable reference of common TCP and UDP ports. Look up a port number or service name to see what runs there, which range it belongs to, and any security notes. It is a lookup table for learning and reference, not a tool that actually scans hosts.
FreeOnline Tool
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How to Use
- Type a port number, such as 80 or 443, or a service name, such as HTTP or SSH, into the search box.
- Read the service name, protocol, and description for that port.
- Browse the categorized list of common ports to learn the default port for each kind of service.
- Use what you find as a reference when writing firewall rules or troubleshooting a network problem.
Features
- Covers the common TCP and UDP ports and the services that use them.
- Search by port number or by service name.
- Separates well-known ports (0-1023), registered ports (1024-49151), and dynamic ports.
- Every entry includes a description of the service and where you would typically meet it.
- Flags high-risk ports with a security note.
Use Cases
Writing least-privilege firewall rules
Use the port reference to open only the ports your service genuinely needs and close everything else.
Troubleshooting connection failures
When a service will not connect, check the expected port to work out whether something else is using it or a firewall is in the way.
Studying network security
Learn the default ports of common services to understand what port scanning is looking for and how attack surface is assessed.
Planning a service deployment
Check the common ports before rolling out a new service so its listener does not collide with something already running.
FAQ
Why does knowing port numbers matter?
Ports distinguish the different services running on one machine. Knowing which port belongs to what helps you write firewall rules, debug connection failures, and recognize risky exposure.
Which ports should I close on my firewall?
Anything that does not need to be reachable from outside, especially Telnet (23), FTP (21), RDP (3389) when unused, and SMB (445). Open only the minimum set your service actually requires.
How do I find the process holding a port?
On Windows run netstat -ano | findstr :PORT. On macOS or Linux run lsof -i :PORT or ss -tlnp | grep PORT. Once you have the PID you can inspect the process further.
Why is HTTP on port 80 and HTTPS on 443?
These are well-known port assignments defined by IANA. Browsers have the protocol-to-port mapping built in, which is why you can omit the port from a URL when the default is used.