Port 249 has no service. It carries nothing. For 35 years, it has been marked "Reserved" by IANA, held aside for special purposes that never came.1
What Reserved Means
The Internet's port numbers exist in three states: Assigned (in use by a protocol), Unassigned (available for assignment), and Reserved (held back for special purposes).
Port 249 falls into that third category. It lives in the well-known port range (0-1023)—the most prestigious address space on the Internet—but has never been given a protocol to serve.
The History
RFC 1060, published in March 1990 by Jon Postel and Joyce K. Reynolds, documented the assigned numbers that made the Internet work.2 In that document, ports 249-254 were listed as "Unassigned" and port 255 was marked "Reserved."
Over time, the entire range of 249-255 became Reserved. As of December 2024, IANA still lists these ports as Reserved, referencing RFC 1060.3
Why Reserve Ports?
According to RFC 6335, which governs how IANA manages port numbers, Reserved ports serve special purposes.4 They're often held at the edges of port ranges—values like 0, 1023, 1024—in case those ranges need to be extended or the overall port number space needs to be restructured.
Ports 249-255 sit near the top of the well-known range. They were set aside as a buffer, a space to grow into if needed. That need never came.
What Listens Here?
Nothing should be listening on port 249. It's Reserved, which means it's not available for regular assignment. No protocol has claimed it. No service runs here by design.
But computers don't always follow the rules. To check what's listening on port 249 on your system:
Linux/Mac:
Windows:
If something appears, it's either a misconfigured service or malware using an unusual port to avoid detection.
The Unassigned Ports
Port 249 is a reminder that the Internet was designed with room to grow. The architects who built the port numbering system didn't assign every number immediately. They left gaps, reserves, spaces for future protocols that might need a home.
Most of those spaces have been filled. Port 249 and its neighbors remain empty—a small, silent buffer zone that has never been crossed.
Frequently Asked Questions
Related Ports
- Port 255: Also Reserved, marks the end of the original 8-bit port space
- Ports 250-254: Reserved alongside port 249 since RFC 1060
- Port 0: Reserved, used to request "any available port" in some systems
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