Port 336 is unassigned. Both TCP and UDP on port 336 have no official service designation in the IANA registry.1
What This Means
The Internet has 65,535 possible port numbers (0-65535). They're divided into three ranges:
- Well-Known Ports (0-1023): Reserved for system services, assigned by IANA through IETF review
- Registered Ports (1024-49151): Available for user applications, less formal registration
- Dynamic/Private Ports (49152-65535): Ephemeral ports used for temporary connections
Port 336 sits in the well-known range. This is prime real estate—ports here are meant for fundamental Internet services. Port 22 is SSH. Port 80 is HTTP. Port 443 is HTTPS.
Port 336 is none of those things. It's reserved but unclaimed.2
Why Unassigned Ports Exist
Not every well-known port has a tenant. The IANA maintains the registry, but services only get assigned when someone builds a protocol important enough to deserve permanent residence in the 0-1023 range.
Port 336 has been unassigned for decades. It's not a gap in the system—it's breathing room. The Internet doesn't need 1,024 well-known services. Most of the ports in this range sit empty, waiting.
Some never get used. That's fine. The registry isn't meant to be full.
What Runs on Port 336
Officially? Nothing.
Unofficially? Maybe something. Just because a port is unassigned doesn't mean it's unused. Custom applications can listen on any port. Malware sometimes picks unassigned ports specifically because they're less monitored.
The Nmap services database lists port 336/tcp as "unknown"—a polite way of saying "we've never seen anything here."3
How to Check What's Listening
If you want to know whether something is using port 336 on your system, use these commands:
On Linux/macOS:
On Windows:
If something appears, it's not an official service. It's either a custom application, a misconfiguration, or something you should investigate.
Why This Port Matters
It doesn't, really. Port 336 isn't carrying SSH connections or serving web pages. It's not part of the Internet's critical infrastructure.
But it exists. It's reserved. And that reservation means something.
When IANA assigns a port, they're saying "this service is important enough to get a permanent address." When a port stays unassigned, it means the need hasn't arrived yet—or maybe never will.
Port 336 is a placeholder. A door that was built but never opened. A reminder that the Internet has room to grow in directions we haven't imagined yet.
Related Ports
Many ports in the well-known range remain unassigned:
- Ports 334-343: Unassigned block
- Port 336 sits in the middle of this range
The ports around it are similarly quiet. No drama. No traffic. Just reserved space in the registry, waiting.
Frequently Asked Questions
The Quiet Ones
Most ports are like port 336. Reserved but unused. Documented but empty.
We talk about the famous ports—22, 80, 443, 25—because they carry the Internet's daily traffic. But for every port that handles millions of connections per second, there are dozens that have never seen a single packet.
Port 336 is one of the quiet ones. It's been waiting in the well-known range since the port system was created, holding space for a service that never came.
Maybe that service will arrive someday. Maybe it won't.
Either way, port 336 will be here, unassigned and patient, a reserved seat at a table where nobody ever sits.
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