Port 290 has no official assignment. No protocol. No RFC. No service listening by default.
It sits in the well-known port range (0-1023)—the ports controlled by IANA, the Internet Assigned Numbers Authority—but it's marked "Unassigned" in the registry.1 It's part of a quiet stretch: ports 288 through 307, most of them empty.
What the Well-Known Range Means
Ports 0-1023 are called the well-known ports or system ports. These are the prestigious addresses of the Internet.2 You need special permission (root access on Unix systems) to listen on them. IANA assigns them through formal procedures—IETF Review or IESG Approval—which means getting a port in this range requires documentation, justification, and consensus.3
Port 22 is SSH. Port 80 is HTTP. Port 443 is HTTPS. These are the famous residents.
Port 290? It's an empty lot between occupied buildings.
What Unassigned Actually Means
"Unassigned" doesn't mean "never used." It means "officially available for assignment upon request."2
Someone could be running a service on port 290 right now—custom software, internal tools, experimental protocols. There's nothing stopping you from binding a process to port 290 on your machine. The difference is that it's not standardized. No one else on the Internet expects to find anything there.
Unassigned ports are the Internet's capacity for growth. They're held in reserve for protocols that don't exist yet, problems we haven't discovered, solutions no one has imagined.
Why Unassigned Ports Matter
The Internet has 65,535 ports per protocol (TCP and UDP). Only a fraction are assigned. Port 290 represents the strange reality that most of the Internet's address space is empty.
This emptiness is intentional. When Jon Postel designed the port number system in the early 1980s, he created far more addresses than were needed at the time. It seemed excessive. It turned out to be prescient.
Every protocol we rely on today—HTTPS, IMAP, BitTorrent, WebRTC—needed a port number when it was created. The unassigned ports were there waiting. Port 290 is part of that reserve capacity.
How to Check What's Listening
Even though port 290 has no official assignment, something could be listening on it on your machine. Here's how to check:
On Linux or macOS:
Or:
On Windows:
If you see output, something is bound to port 290. If not, the port is closed—which is what you'd expect for an unassigned port.
The Honest Truth
There's no dramatic story here. No brilliant engineer solving a critical problem. No protocol carrying the world's traffic.
Port 290 is simply unused. It's part of the Internet's infrastructure in the same way that blank pages are part of a book's structure—they create space for what comes next.
Most ports are like this. The assigned ones get the attention, but the unassigned ones make the system possible. They're the reason the Internet can evolve without running out of addresses.
Port 290 is waiting. That's its purpose.
Related Ports
The well-known port range (0-1023) contains many unassigned ports. Port 290's neighbors in the 288-307 range are mostly empty.1 Some notable assigned ports nearby:
- Port 280: http-mgmt (HTTP management)
- Port 308: Novastor Backup
- Port 311: Mac OS X Server Admin
- Port 389: LDAP (Lightweight Directory Access Protocol)
Frequently Asked Questions
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