Port 3523: Odeum Serverlink — A Ghost in the Registry

What This Port Is

Port 3523 sits in the registered ports range (1024-49151). IANA maintains this range for software vendors and developers who formally request a port number for their application. Unlike the well-known ports below 1024, registered ports don't require elevated privileges to open, and unlike ephemeral ports above 49151, they're meant to be stable identifiers for specific services.

In June 2002, IANA assigned port 3523 to Odeum Serverlink (service name: odeumservlink), registered for both TCP and UDP. The software appears to have been an early-2000s digital media or streaming product. The company and software are no longer active. No documentation, source code, or surviving installations are readily discoverable today.

This is not unusual. The registered port space is a graveyard of products from the dot-com era: registered with good intentions, abandoned when companies folded or pivoted, but never formally released back into the pool. IANA's registry doesn't expire assignments.

What You'll Actually Find on This Port

Almost certainly nothing official. If something is listening on port 3523 on your machine or network, it isn't Odeum Serverlink. It's one of:

• A development server that picked a high-numbered port to avoid conflicts
• A game, peer-to-peer application, or custom internal tool
• Malware (worth investigating if unexpected)

The registered assignment provides no meaningful protection. Any process can bind to port 3523.

How to Check What's Using This Port

On Linux or macOS:

# Show what process is listening on port 3523
ss -tlnp sport = :3523

# Or with lsof
lsof -i :3523

On Windows:

netstat -ano | findstr :3523

Then cross-reference the PID in Task Manager or with tasklist /fi "PID eq <pid>".

Remotely (checking if the port is open on another host):

nc -zv hostname 3523
# or
nmap -p 3523 hostname

Why Unassigned-in-Practice Ports Matter

The registered port range contains over 48,000 numbers. Only a fraction are in active, widespread use. The rest exist in a state like port 3523: technically claimed, practically open.

This matters because:

• Firewall rules: Blocking or allowing "registered ports" as a category is meaningless. Each port needs individual evaluation.
• Security scanning: An open port 3523 on an unexpected host warrants investigation, precisely because there's no obvious legitimate service to expect there.
• Port selection for new services: Developers sometimes assume a registered-but-dormant port is safe to reuse informally. It usually is, but it can cause confusion if anyone checks against the IANA list.

The honest summary: port 3523 is a reserved seat for a guest who never comes back. In practice, it's free real estate.