Port 813 exists in the well-known ports range—the Internet's most carefully controlled address space—but appears to have no official IANA assignment. It's a door that was built but never opened.
What Range This Port Belongs To
Port 813 sits in the well-known ports range (0-1023), also called system ports. This is the Internet's restricted zone. Ports in this range are:
- Assigned only by IANA (Internet Assigned Numbers Authority)
- Typically require root or administrator privileges to listen on
- Reserved for standardized services that needed global recognition
The assumption was that these 1,024 ports would fill up with essential protocols. But not all of them did.
What Well-Known Means
When the port system was designed, the architects imagined a future with hundreds of globally standardized services—each needing a universally recognized port number. They set aside the first 1,024 ports for this purpose.
Some filled immediately: port 80 for HTTP, port 25 for SMTP, port 22 for SSH. These became the infrastructure of the Internet.
Others, like port 813, were never claimed. The space was reserved, but no service stepped forward to occupy it officially.
Why This Port Has No Assignment
There are several reasons a well-known port might remain unassigned:
The service never materialized — Someone may have planned a protocol that never got built, or a standard that never gained adoption.
The number wasn't requested — Protocol designers might have requested different port numbers, or used the registered ports range (1024-49151) instead.
Historical artifact — Early Internet architecture reserved this entire range optimistically, assuming more standardization than actually occurred.
The result: gaps in the well-known range where ports exist but carry nothing official.
Could Something Be Using This Port Anyway?
Yes. Just because IANA hasn't assigned port 813 doesn't mean it's never used.
Unofficial software might use port 813 for internal communication, custom applications, or proprietary protocols. There's no global registry preventing this—just the understanding that using an unassigned well-known port is risky because IANA could assign it at any time.
Malware sometimes uses random or uncommon ports to avoid detection. An unassigned port like 813 could be attractive for this reason—it's in the "official" range but doesn't have standard traffic patterns.
Local services on your network might use port 813 for anything. Without an official assignment, there's no guarantee what you'll find.
How to Check What's Listening on Port 813
If you want to see if anything on your system is using port 813:
On Linux or macOS:
On Windows:
Using nmap to scan a remote system:
If something responds, investigate what process is bound to that port. It's not a standard service, so it warrants attention.
Why Unassigned Ports Matter
The existence of unassigned ports in the well-known range tells us something about how the Internet actually evolved versus how it was planned.
The architects built a system with room for 65,535 ports per protocol (TCP and UDP). They reserved the first 1,024 for "important" services. But the Internet didn't need 1,024 globally standardized services. It needed dozens of essential ones, and then thousands of application-specific ports that didn't require central coordination.
Port 813 sits in that gap—part of a reserved namespace that assumed a more centralized Internet than the one we built.
The Practical Reality
If you see traffic on port 813, don't assume it's benign because it's in the well-known range. In fact, the opposite: unassigned well-known ports are unusual. Standard services live on assigned ports. Custom applications typically use the registered or dynamic ranges. Traffic on port 813 deserves scrutiny.
It's a door that shouldn't be open unless you know exactly why it is.
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