Port 3191: ConServR SSL Proxy — A Name in the Registry

What This Port Is

Port 3191 sits in the registered port range (1024-49151). These ports are assigned by IANA, the Internet Assigned Numbers Authority, to specific services upon request. Unlike the well-known ports below 1024, registered ports don't require root privileges to use, and their assignments are less rigorously enforced in practice.

IANA lists port 3191 as assigned to ConServR SSL Proxy, attributed to a registrant named Mikhail Kruk. Both TCP and UDP are listed.¹

That's where the trail ends.

The Ghost Registration Problem

ConServR SSL Proxy doesn't appear in any software repository, security advisory, vendor documentation, or meaningful technical discussion. This is more common than you'd think. The registered port range contains thousands of assignments made by developers, small companies, and individuals over the decades. Many of those projects were abandoned, never shipped, or never gained any users. The registry entry persists long after the software has gone quiet.

Port 3191 is one of these. The name suggests a proxy service that wrapped connections in SSL, probably for a product called ConServR. Beyond that, nothing.

If you find port 3191 open on a system you administer, it isn't ConServR SSL Proxy. Something else claimed it.

What's Actually Using It

Any application can bind to port 3191. Because the registered service is defunct, you're more likely to encounter:

• Custom internal applications that picked an available number arbitrarily
• Development servers assigned ports in this range dynamically
• Malware that chose an obscure port to avoid detection

The only way to know is to check.

How to Check What's Listening

On Linux or macOS:

ss -tlnp | grep 3191
# or
lsof -i :3191

On Windows:

netstat -ano | findstr :3191

With nmap (from another machine):

nmap -sV -p 3191 <target-ip>

The -sV flag tells nmap to probe the service and attempt to identify what's actually running, regardless of what IANA says should be there.

Why Unassigned (and Forgotten) Ports Matter

The registered port range was designed to bring order to the chaos of application networking. In practice, it's a historical artifact. Assignments accumulate, services die, and the registry outlives the software it describes.

What this means practically: when you see an unfamiliar port open, the IANA assignment is a starting point, not an answer. Port 3191 says "ConServR SSL Proxy." If you find it open on your server tonight, that tells you nothing useful. Check what's actually there.