What Port 490 Is
Port 490 sits in the well-known ports range (0-1023), officially assigned by IANA to a service called micom-pfs—the MICOM Portable File System protocol.1 Both TCP and UDP can use this port.
That's where the clear information ends. Unlike port 22 (SSH) or port 80 (HTTP), where you can find RFCs, documentation, active implementations, and millions of engineers who know exactly what happens on those ports, port 490 represents something different: a port assignment that has outlived the protocol it was meant to serve.
The Ghost in the Registry
MICOM-PFS appears in the IANA registry. It shows up in network documentation databases. Cisco and Juniper include it in their protocol libraries.23 But try to find documentation about what the protocol actually did, how it worked, or who used it—and you'll come up empty.
The assignment lists David Misunas at MICOM as the contact. But the protocol itself? The portable file system it was meant to support? The problems it solved? Those details have been lost to time.
This is the archaeological layer of the Internet. Port 490 was assigned when the port registry was smaller, when getting a well-known port number meant your protocol mattered enough to warrant permanent infrastructure space. Someone at MICOM built something. Someone at IANA approved it. And then the world moved on.
What "Well-Known Port" Means
Ports 0-1023 are the well-known ports, assigned by IANA for standardized services. Getting a well-known port assignment historically meant your protocol was important enough to deserve a permanent, universally recognized number.
Port 490's presence here suggests micom-pfs mattered once. It was significant enough to claim a spot in the registry. But unlike its neighbors—protocols that became foundational to the Internet—micom-pfs didn't survive.
What Actually Uses Port 490 Today
Realistically? Almost nothing.
You might find:
- Legacy systems that still have the port listed in configuration files nobody's looked at in 20 years
- Security scanners checking if port 490 is open (because it's in the registry)
- Reference implementations in networking libraries that include every IANA-assigned port4
You will not find active MICOM Portable File System traffic. The protocol is, for all practical purposes, extinct.
How to Check What's Listening
If you want to see if anything is actually using port 490 on your system:
On Linux/macOS:
On Windows:
If something is listening on port 490, it's worth investigating. It's probably not micom-pfs. It might be:
- A modern application using an "unoccupied" well-known port
- Malware hiding in an obscure port assignment
- A misconfigured service
Why Unassigned (or Forgotten) Ports Matter
Port 490 isn't technically unassigned—it has an official designation. But functionally, it might as well be. The protocol is gone. The assignment remains.
This matters because:
The registry is permanent. IANA doesn't reclaim port assignments just because a protocol becomes obsolete. Port 490 will be "micom-pfs" in the registry long after the last person who understood the protocol is gone.
It creates namespace scarcity. There are only 1,024 well-known ports. Port 490 occupies one of those slots for a protocol nobody uses. Modern protocols that might benefit from a well-known port assignment have to use higher-numbered registered ports instead.
It's a historical record. Every assigned port tells a story about what people thought was important enough to standardize. Port 490 says: in the early days of networking, portable file systems mattered enough to get permanent infrastructure space. The protocol failed, but the record remains.
The Honest Truth
Port 490 is a tombstone. It marks something that existed, mattered briefly, and vanished. The IANA registry is full of these—port assignments that outlived their protocols, service names that mean nothing to anyone alive today.
It's not dramatic. Nobody's SSH session depends on port 490. No website breaks if you block it. It's just there, in the registry, a reminder that the Internet we use today is built on top of hundreds of failed experiments, forgotten protocols, and abandoned ideas.
Someone at MICOM thought their portable file system was important enough to request a well-known port. IANA agreed. And now, decades later, the port remains while the protocol has faded into obscurity.
That's port 490. A name without a protocol. A number without traffic. A piece of Internet history that almost nobody remembers.
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