Port 3107: RDI Business Protocol — Assigned in Name Only

What Port 3107 Is

Port 3107 sits in the registered port range — ports 1024 through 49151, the middle tier of the port numbering system. This range sits between the well-known ports (0-1023, reserved for foundational protocols like HTTP, DNS, and SSH) and the ephemeral ports (49152-65535, used for temporary outbound connections).

IANA's registry lists port 3107 as "RDI Business protocol."¹ That is the entire official record. No RFC defines it. No specification documents it. No company has publicly claimed it. The entry exists, but the protocol behind it — if it ever existed — left no trace.

The Registered Port System

Registered ports aren't assigned the way well-known ports are. Anyone can submit a request to IANA claiming a port for a service. If the request passes basic review, IANA adds it to the registry. The registry is meant to help organizations avoid collisions, not to guarantee that every listed protocol is real, documented, or still in use.

The result: thousands of registered port entries like 3107, where someone claimed a port for an internal or commercial system that was never published, never standardized, and eventually abandoned — leaving only the name behind.

This isn't a flaw in the system. It's the system working as designed. The alternative — requiring full documentation before any port can be reserved — would make informal development impossible.

Known Unofficial Uses

No widely-observed unofficial use for port 3107 has been documented. One port database notes that the 3074-3174 range has been seen in connection with Rainbow Six Vegas gaming traffic², but this is a broad range association, not specific to 3107.

If you see traffic on port 3107, it is almost certainly application-specific — a custom internal service, a development tool, or a commercial product that chose this port without consulting the registry.

How to Check What Is Listening on This Port

On Linux or macOS:

# Show what process is listening on port 3107
sudo lsof -i :3107

# Alternative using ss
sudo ss -tlnp | grep 3107

On Windows:

netstat -ano | findstr :3107

The output will include the process ID (PID). Cross-reference it against your process list to identify what is actually using the port.

Why Unassigned Ports Matter

The port number system works because applications agree on where to find each other. When a protocol is well-known and documented — HTTP on 80, SSH on 22 — clients know where to connect before any negotiation happens.

Unassigned or nominally-assigned ports like 3107 are the gaps and placeholders in that system. They matter precisely because they're empty: they're the space where custom applications land, where developers point services during testing, and where the registry's good intentions meet the messiness of how software actually gets built.

If something shows up on port 3107 on your network, the registry won't tell you what it is. That's the honest answer — and the reason checking with lsof or ss matters more than consulting any port list.