Port 1783: The Decommissioned Port

Port 1783 sits in an unusual category: not unassigned, but formerly assigned. IANA records show it was once registered under the name "naonao," then decommissioned on April 14, 2000. Whatever naonao was — a protocol, a product, a company — it left no public record. The registration simply expired, and the port returned to the pool of available numbers.

What Range This Port Belongs To

Port 1783 falls in the registered ports range (1024–49151). This range is managed by IANA and was historically used for applications that requested a dedicated port number. Unlike the well-known ports (0–1023), registered ports don't require elevated system privileges to bind, and assignment was once available to any organization that submitted a request.

The registered range was, for a time, treated like real estate — you could stake a claim. Many of those claims were never developed. IANA periodically decommissions registrations when the associated service is no longer active or verifiable.

What Runs on Port 1783 Today

Nothing official. No protocol, no service.

In practice, any application can use port 1783 for its own purposes. It might appear in:

• Custom enterprise applications that chose a port at random (or by design)
• Gaming servers picking from the registered range
• Development environments using it as a test port
• Malware or scanners probing registered ports opportunistically

If you're seeing traffic on port 1783 on your network, it's application-specific — not a standard protocol.

Checking What's Listening on This Port

To see if anything is using port 1783 on your machine:

macOS / Linux:

# Show processes listening on port 1783
lsof -i :1783

# Or with ss (Linux):
ss -tlnp sport = :1783

Windows:

netstat -ano | findstr :1783

The output will show the process ID (PID) if something is listening. On macOS and Linux, lsof also shows the process name directly.

Why Decommissioned Ports Matter

The registered port range was never infinite — 48,128 ports sounds like a lot until you consider how many applications want a permanent home. IANA decommissions stale registrations to keep the registry accurate and to make ports available for new assignments.

Port 1783 is a reminder that the port registry is a living document, not a permanent ledger. Services come and go. Registrations lapse. The port that "naonao" claimed in the 1990s is now available again, waiting for whatever comes next.

• IANA Service Name and Transport Protocol Port Number Registry
• SpeedGuide Port 1783