Port 3676: va-pacbase — The Ghost of IBM's Mainframe CASE Tool

What Runs on Port 3676

Port 3676 is officially registered to va-pacbase — the VisualAge Pacbase server. It was registered with IANA in January 2003 by Dominique Lelievre at IBM France, assigned to both TCP and UDP.¹

If you see this port active today, it's almost certainly not Pacbase. It's something else that chose the number opportunistically, or a scanner artifact. VisualAge Pacbase was discontinued by IBM around 2015 and carries a "Not Supported" designation.²

What VisualAge Pacbase Was

Pacbase was a CASE tool — a Computer-Aided Software Engineering system — designed for mainframe application development. It originated in 1983 at a French company called CGI Informatique. IBM acquired CGI in 1993 and rebranded the product as VisualAge Pacbase in 1997.²

The tool's core trick: developers wrote in the Pacbase language, and the system generated COBOL. Not compiled it — generated it. Pacbase sat one level of abstraction above COBOL, producing structured code that would run on z/OS, Windows, and UNIX systems.

It was widely adopted in European banking and insurance during the 1980s and 1990s, industries that needed structured, auditable, mainframe-grade applications. For those shops, Pacbase wasn't a curiosity — it was infrastructure.

Port 3676 would have handled the client-server communication between developer workstations and the central Pacbase repository server: checking out components, validating changes, triggering code generation across the development environment.

The Registered Ports Range

Port 3676 sits in the registered ports range (1024–49151). IANA manages this space — organizations and vendors can formally register port numbers for their software so that different applications don't collide.¹

Registration is permanent by convention. IANA doesn't reclaim port numbers when software is abandoned. This means the registered port space contains decades of ghost assignments: software that has been discontinued, acquired, rebranded, or simply forgotten. Port 3676 is one of thousands in that category.

What to Do If You See Port 3676 Open

If port 3676 is listening on a system you manage, it isn't Pacbase. Check what's using it:

macOS / Linux:

lsof -i :3676
ss -tlnp | grep 3676

Windows:

netstat -ano | findstr :3676
Get-Process -Id (Get-NetTCPConnection -LocalPort 3676).OwningProcess

Identify the process before deciding whether to allow or block it. An unrecognized process on any registered port warrants investigation.