Port 823 exists, but nothing lives there.
It's officially unassigned by the Internet Assigned Numbers Authority (IANA).1 No protocol claims it. No service runs on it by default. It's one of hundreds of ports that sit quietly in the registry, available but unused.
What "Unassigned" Means
Ports are divided into three ranges:
- Well-known ports (0–1023) — Reserved for system services, assigned by IANA
- Registered ports (1024–49151) — Available for user processes, registered with IANA
- Dynamic/ephemeral ports (49152–65535) — Temporary ports assigned automatically by the operating system
Port 823 falls in the well-known range—the first 1,024 ports that traditionally belong to critical services like HTTP (80), HTTPS (443), and SSH (22). These ports require root/administrator privileges to bind to on most systems.
But port 823? Nobody needs it. At least not yet.
The Gap in the Registry
Ports 811–827 are all unassigned.1 That's seventeen consecutive ports in the well-known range just sitting there. Not because they were overlooked, but because the Internet doesn't need them yet.
This is intentional. IANA doesn't assign ports speculatively. A port gets an assignment when someone creates a protocol or service that genuinely needs a permanent home. Until then, the port waits.
What Might Be Listening
Just because port 823 has no official assignment doesn't mean nothing uses it. Custom applications, internal services, and proprietary protocols can (and do) use unassigned ports.
To check what's listening on port 823 on your system:
Linux/Mac:
Windows:
If you see something listening there, it's not a standard service. It's either:
- A custom application someone configured to use that port
- Malware (less likely, but worth investigating)
- A service that chose an unassigned port to avoid conflicts
Why Unassigned Ports Matter
The existence of unassigned ports is a feature, not a bug. They represent:
Flexibility — New protocols can claim well-known ports when needed
Room to grow — The Internet's nervous system has spare capacity
Stability — Assignments aren't made casually; they're reserved for services that last
Port 823 might remain unassigned forever. Or fifty years from now, it might carry a protocol we can't yet imagine. Either way, it's there—a door waiting for a purpose.
Related Ports
The unassigned block around port 823 includes:
- Ports 811–827 — All currently unassigned1
For comparison, nearby assigned ports:
- Port 443 — HTTPS (encrypted web traffic)
- Port 993 — IMAPS (encrypted email retrieval)
Frequently Asked Questions About Port 823
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