Port 2663: BinTec-TAPI — A Registered Port Nobody Talks About

What Port 2663 Is

Port 2663 is registered with IANA for BinTec-TAPI — a service from BinTec, a German networking equipment company now operating as Bintec elmeg, part of the Teldat Group.¹

TAPI stands for Telephony Application Programming Interface, a Windows standard that lets software communicate with telephony hardware — desk phones, PBX systems, modems, ISDN adapters. BinTec built routers and gateways that supported ISDN and analog telephony alongside data networking, and port 2663 was how their equipment exposed TAPI functionality to Windows clients on the network.

Both TCP and UDP are listed for this port in the IANA registry.²

The Registered Port Range

Port 2663 sits in the registered ports range: 1024–49151.

Well-known ports (0–1023) are reserved for foundational protocols — HTTP at 80, HTTPS at 443, DNS at 53. No one needs to ask permission to use those; they are part of how the Internet works.

Registered ports are different. Anyone — a company, an individual, an open-source project — can apply to IANA to claim a port number for a specific service. IANA records the assignment. That recording does not mean the service is widely used, actively maintained, or will ever touch your network. It means someone filed the paperwork.

The registered range contains roughly 48,000 ports. Most of them look like port 2663: a specific piece of software, a specific era, a specific problem that needed solving. They are a catalog of every network service that mattered enough to someone, somewhere, to formalize.

Why You Might See It Open

You almost certainly will not. BinTec's TAPI integration was an enterprise product aimed at European businesses running ISDN telephone systems alongside their routers — a configuration that was common in Germany in the late 1990s and early 2000s and is now largely gone, replaced by VoIP.

If port 2663 appears open on a system today, the most likely explanations are:

• A BinTec or Bintec elmeg device still in service on a legacy network
• A network scanner misidentifying traffic on a nearby port
• Something unrelated that happened to bind to this port

Ports are not reserved in memory. If no service is using 2663 on a given machine, an application can open it. The IANA registration is advisory, not enforced.

How to Check What Is Listening

On Linux or macOS:

# Show which process is using port 2663 (TCP)
sudo lsof -i TCP:2663

# Or with ss (Linux)
ss -tlnp | grep 2663

On Windows:

netstat -ano | findstr :2663

The last column of netstat output is the process ID. Cross-reference it with Task Manager or tasklist to identify the application.

If nothing is listening, these commands return no output. That is the expected result on almost every modern machine.