Port 3672: HarlequinORB — A Reserved Ghost from CORBA's Era

What This Port Is

Port 3672 is registered with IANA under two names: harlequinorb and lispworks-orb. Both names refer to the same thing — a CORBA-compliant Object Request Broker (ORB) built in Common Lisp, originally by a British software company called Harlequin, later continued under the LispWorks brand.¹

It belongs to the registered port range (1024–49151). These ports are not reserved by the operating system for privileged processes the way well-known ports (0–1023) are. Anyone can use them without elevated permissions. But IANA keeps a registry of which ones have been claimed by specific applications, and 3672 has been claimed since the late 1990s.

What HarlequinORB Was

CORBA — the Common Object Request Broker Architecture — was the distributed computing standard of the 1990s. The idea: objects running on different machines, written in different languages, could call methods on each other transparently. Your Java client could invoke a method on a C++ server or a Common Lisp server, and CORBA would handle the serialization, the network transport, the type negotiation — all of it.

Harlequin built a CORBA ORB entirely in Common Lisp. The ORB let developers construct three-tier client-server applications in Lisp while staying interoperable with the rest of the CORBA world through IIOP, the Internet Inter-ORB Protocol. A Java GUI could talk to a Common Lisp backend through standard CORBA interfaces.²

Harlequin later became LispWorks. LispWorks still exists and still ships a CORBA ORB. But CORBA itself has been largely supplanted — first by SOAP and XML-RPC, then by REST, then by gRPC and similar approaches. The complexity that CORBA promised to hide turned out to be the complexity that killed it.

The port reservation is a fossil record of that era.

What You'll Find on Port 3672 Today

Almost certainly nothing related to CORBA or LispWorks. If something is listening on port 3672 on a system you're examining, it's far more likely to be:

• A custom application that picked this port arbitrarily
• A game server or peer-to-peer application using it by convention
• Malware (any port can be used by any process — IANA registration is voluntary, not enforced)

The IANA registry is a coordination mechanism, not an access control system. Any process can open any port. Registration just means "we told IANA we use this."

How to Check What's Listening

On Linux or macOS:

# Show the process listening on port 3672
sudo lsof -i :3672

# Or with ss (Linux):
sudo ss -tlnp | grep 3672

# Or with netstat:
netstat -an | grep 3672

On Windows:

netstat -ano | findstr :3672
# Then look up the PID in Task Manager, or:
tasklist /fi "pid eq <PID>"

If nothing comes back, nothing is listening. That's the most likely result.

Why Registered-but-Dormant Ports Exist

The registered port range has over 48,000 slots. Many were claimed by software products that no longer ship, companies that no longer exist, or protocols that never gained adoption. IANA doesn't reclaim ports from defunct projects — deregistration is a deliberate process that rarely happens.

This creates a landscape of archaeological layers: ports reserved for IRC bots from 2003, enterprise middleware from 1997, database appliances discontinued a decade ago. Port 3672 is one of them — not unassigned, but effectively unused. A placeholder for a distributed computing dream that came, competed, and mostly lost.