Port 3667: IBM Information Exchange — A Registered Port for a Quieter Era

What Port 3667 Is

Port 3667 is a registered port, assigned by IANA to IBM Information Exchange (service name: infoexch) in January 2003.¹

Registered ports live in the range 1024 to 49151. Unlike the well-known ports below 1024, which require root or administrator privileges to bind, registered ports can be opened by ordinary applications. Unlike ephemeral ports (49152 and above), which are handed out dynamically for outgoing connections, registered ports are documented: a specific organization asked IANA for the number and received it.

Port 3667 was one of those requests.

What IBM Information Exchange Was

IBM Information Exchange was part of IBM's EDI software family. EDI, Electronic Data Interchange, is the decades-old standard for machine-to-machine business communication: purchase orders, invoices, shipping notices, all structured and exchanged without a human touching them. Before APIs, before JSON, before the web made everything programmable, EDI was how large companies talked to each other.

IBM built EDI tools for their platform ecosystem throughout the 1980s and 1990s — AS/400, mainframes, PS/2. The expEDIte series of translators converted business data into standard EDI formats across these systems.² By the time IANA registered port 3667 in 2003, the broader industry was already moving toward web-based integration. The port arrived late.

There are no known unofficial uses for port 3667. It is not associated with any common malware, gaming traffic, or developer tools.

What to Do If You See Port 3667

If something is listening on port 3667 on your system, it is almost certainly not IBM Information Exchange. Identify it:

On Linux or macOS:

sudo lsof -i :3667
sudo ss -tlnp sport = :3667

On Windows:

netstat -ano | findstr :3667

Then cross-reference the process ID against your running processes. If you don't recognize what's there, that's worth investigating.

Why Registered Ports Matter

The registered port range exists so that software can claim a consistent, predictable address. A client connecting to port 3667 knows, at least in principle, what it will find there.

In practice, the registry is a historical record as much as it is a live directory. Services get registered, products get discontinued, and the port numbers remain in the table. Port 3667 is registered. The software it was registered for has largely faded from active use. The number sits quietly, documented, waiting for a connection that rarely comes.