Port 316 is officially assigned to decAuth (DEC Authentication), a protocol from Digital Equipment Corporation. Both TCP and UDP port 316 carry this designation in the IANA registry.12
The protocol itself has vanished. No RFC. No specification. No documentation that survives in any searchable form online.
What decAuth Was
The name tells us what it did: authentication for Digital Equipment Corporation systems. DEC, founded in 1957, became one of the most important computer companies of the 1970s and 1980s.3 Their VAX minicomputers and DECnet networking protocol connected business and research facilities worldwide.4
In the mid-1980s, network security became critical for DEC as hackers began attacking their systems.5 They needed authentication. They built decAuth. They registered port 316 with IANA. Michael Agishtein was listed as the assignee.1
Then Digital Equipment Corporation was acquired by Compaq in 1998. Compaq was acquired by HP in 2002. Somewhere in those transitions, decAuth disappeared. The systems that spoke it were decommissioned. The documentation was lost or archived where search engines cannot reach it. The protocol died.
But the port number remains.
The Well-Known Ports Range
Port 316 sits in the well-known ports range (0-1023), system ports assigned by "IETF Review" or "IESG Approval" procedures.6 These are the reserved seats of the Internet—once you have one, you keep it. Even if the service dies. Even if the company dies.
This is why port 316 will always be decAuth, even though nothing answers there anymore.
Security Notes
Port 316 has been flagged in security databases as having been used by malware in the past.7 This does not mean the port itself is dangerous—it means that because the port sits unused, malware authors occasionally claimed it for covert communication.
An empty house attracts squatters.
How to Check What's Listening
If you want to see if anything is actually using port 316 on your system:
On Linux or macOS:
On Windows:
Most likely, you will find nothing. Port 316 is assigned but unused—a reserved space for a protocol that no longer exists.
Why Unassigned Ports Matter
Port 316 is technically assigned, but functionally it might as well be unassigned. This distinction matters for the architecture of the Internet.
The IANA port registry is a historical record as much as it is a technical specification. Every assigned port tells a story about what people were building, what problems they were solving, what companies were dominant at the time. Port 316 tells the story of Digital Equipment Corporation's brief dominance in networking, and its complete disappearance.
Unassigned ports (and effectively dead assigned ports like this one) serve another purpose: they remind us that the Internet's namespace is finite. There are only 65,535 possible port numbers. The well-known range (0-1023) is even smaller. Once you assign a number, it stays assigned, even if the service dies.
This is why modern protocols increasingly multiplex over a small number of standard ports (like 80 and 443 for HTTP/HTTPS) rather than requesting new port assignments. The namespace is filling up, and we cannot reclaim the tombstones.
Related Ports
Other DEC-related ports in the well-known range include:
- Port 260: Unassigned (formerly used for DEC systems)
- Port 261-279: Reserved for various DEC protocols
- Port 310-313: Reserved for other DEC services
Many of these share decAuth's fate: officially assigned, functionally extinct.
Frequently Asked Questions
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