This page documents exactly how the reference is produced, so you can judge whether a page applies to your environment.
Data source
The source is the IANA Service Name and Transport Protocol Port Number Registry, downloaded as CSV. The registry is authoritative for service names, transport protocols and assignees. PortAtlas reads every row, removes rows marked Reserved, Unassigned, De-registered or Removed, and merges the remaining rows that share a port number.
One page per port number
A single number can have different services on TCP and UDP. Pages therefore list each transport separately whenever the names differ, and the service name shown in the title is the one a reader is most likely searching for. This is why port 512 shows exec for TCP and biff, comsat for UDP rather than pretending one name covers both.
Which ports get a page
Well-known ports (0-1023) are kept when the registry names a service or gives a description. Registered ports (1024-10000) need a service name plus a description of at least 25 characters, unless the number is on a curated list of high-intent ports. High ports need a description of at least 15 characters, plus a short allowlist of famous services. The goal is a useful reference rather than a copy of every placeholder row.
Risk ratings
Ratings describe how much damage an exposed listener can cause, not whether a specific vulnerability exists today.
- High: remote code execution, credential theft, unauthenticated administrative access, or a service that is routinely mass-scanned and exploited.
- Medium: sensitive data or authentication exposure that usually needs credentials, configuration mistakes, or an additional condition to be abused.
- Low: limited impact, local-only by convention, or a service that is normally safe when patched and correctly configured.
A rating is not a CVE assessment and does not replace a vulnerability scan of the software actually running on the port.
Commands and caveats
Linux checks use ss with the flags for each registered transport (-t, -u, -S, -d). Windows checks use Get-NetTCPConnection and Get-NetUDPEndpoint. Block commands use UFW and iptables on Linux. UFW and the built-in Windows cmdlets handle TCP and UDP only; SCTP and DCCP require iptables or nftables and kernel support. The iptables examples are IPv4 rules; mirror them with ip6tables when IPv6 is enabled.
Community conventions
Some widely used ports are not assigned by IANA, such as development servers and application defaults. These pages are marked Community convention and state that another application may legitimately use the same number. They are included because readers search for them, not because the registry assigns them.
Update cadence and corrections
Pages are regenerated from the registry snapshot bundled with each build, and the build date appears in the footer of every page. If the registry and a page disagree, the registry wins. Verify current assignments at IANA before you change firewall policy.
Last updated 2026-10-30.