What Port 3643 Is
Port 3643 sits in the registered port range (1024–49151). These ports are not claimed by the operating system itself — that's the well-known range below 1024, reserved for foundational protocols like HTTP, SSH, and DNS. But they're not random either. IANA maintains a registry for this range, and developers can formally request a port number for their software.
In November 2002, Morten Mertner registered port 3643 for AudioJuggler, a suite of audio utilities — recorder, CD grabber, converter, and burner — from a small European software shop at pianosoft-europe.com.1
That website is now gone. The software left no meaningful trace. The IANA registration remains.
What AudioJuggler Was
AudioJuggler appears to have been a practical collection of audio tools aimed at musicians and music listeners: ripping CDs, recording from sound cards, converting between audio formats. The kind of utility software that thrived in the early 2000s before operating systems started bundling those capabilities natively.
Why it needed a registered port — what network functionality it offered over TCP or UDP — is unclear. Many small software projects registered ports optimistically, anticipating network features that were planned or imagined. Whether AudioJuggler ever actually used 3643 for live traffic is unknown.
What This Port Looks Like Today
If you scan port 3643 on a system and find something listening there, it is not AudioJuggler. It is something else — a local service, an application that chose this port for convenience, or a misconfigured process. The original claimant is gone.
To check what is actually using this port on your machine:
On Linux or macOS:
On Windows:
If nothing is listening, the port is quiet and available. If something is listening, look up the process ID and identify what opened it.
Why Ghost Ports Matter
The registered range has tens of thousands of entries. A meaningful portion of them are like this — software that existed briefly, found few users, and disappeared, leaving a permanent mark in the registry. IANA does not reclaim ports. The table grows in one direction.
This matters for network administrators. A firewall rule based purely on port numbers assumes those numbers mean something consistent. Port 3643 is "AudioJuggler" on paper. In practice, it is unclaimed territory. Any application can open it. Any service can listen on it. The registration is a historical artifact, not a guarantee of what traffic you'll actually see.
The registered range is less a curated list and more a ledger of intentions, some fulfilled and many not.
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