Port 1814: TDP Suite — The proxy neighbor nobody talks about

What Port 1814 Is

Port 1814 belongs to the registered port range (1024–49151). These ports are assigned by IANA to specific services, distinguishing them from the well-known ports (0–1023) that require root privileges to bind, and the ephemeral ports (49152–65535) that operating systems hand out dynamically for outbound connections.

IANA's registry lists port 1814 as belonging to TDP Suite, available on both TCP and UDP. That's where the official record ends. There's no RFC, no public documentation, no known product that identifies itself as TDP Suite. The registration exists, the name occupies the slot, and the rest is silence.¹

The Real World: RADIUS Proxy

Port 1814's actual significance comes from RADIUS, the authentication protocol that enterprise networks depend on. The RADIUS family occupies three consecutive ports:

• 1812 — RADIUS authentication
• 1813 — RADIUS accounting
• 1814 — RADIUS proxy (source port used by FreeRADIUS when acting as a client)

When FreeRADIUS proxies authentication requests — forwarding them from one RADIUS server to another — it needs a source port to send packets from. Port 1814 is what FreeRADIUS uses by convention in that role. The server becomes a client, and 1814 is the port it speaks from.²

This isn't a formal IANA assignment for RADIUS proxy. It's a practical convention that emerged from FreeRADIUS's implementation. If you see port 1814 active on a network server, a RADIUS proxy configuration is the most likely explanation.

What's Listening Here

To check what's using port 1814 on your system:

# Linux/macOS
sudo ss -tulnp | grep 1814
sudo lsof -i :1814

# Windows
netstat -aon | findstr :1814

If you find something listening and you're not running a RADIUS proxy, investigate. Unexpected listeners on registered ports occasionally indicate misconfiguration — or something that shouldn't be there.

Why Unassigned Ports Matter

The registered range exists to prevent chaos. When an application needs a stable, well-known port, it registers with IANA. That registration means other applications know to stay away, and firewall rules can be written with confidence.

The problem is that IANA's registry is only as useful as the information it contains. Port 1814's "TDP Suite" entry occupies space without illuminating anything. The real behavior on this port — FreeRADIUS proxy traffic — emerged independently of the registry, through convention rather than formal assignment.

This happens throughout the registered range. Ports accumulate names from registrations that predate documentation standards, or from software projects that dissolved before the Internet caught up with them. The registry is a historical document as much as an authoritative one.