Port 340: Unassigned — A Number Waiting for Nothing

Port 340 has no official assignment. It sits in the well-known ports range (0-1023) but has never been allocated to any service or protocol by IANA.

The Unassigned Block

Port 340 belongs to a range of ten consecutive unassigned ports: 334-343.¹ This is unusual in the well-known ports range, where most numbers have been claimed for specific protocols. But not these ten. For decades, no one has needed them.

What "Unassigned" Means

When IANA marks a port as unassigned:

• No official protocol or service is registered to use it
• It's technically available for assignment through the IETF standards process
• Someone could request it, but would need to go through formal review and approval
• In practice, it remains empty because no widely-adopted protocol has needed it

This is different from "reserved" ports (held back for special purposes) or "assigned" ports (actively used by registered services).

Why These Ports Exist

The well-known ports range was established when the Internet was young. Port numbers were allocated as protocols were standardized. Some numbers got claimed immediately (22 for SSH, 25 for SMTP, 80 for HTTP). Others never found a purpose.

Port 340 and its neighbors fell into that second category. No RFC ever specified them. No protocol designer ever requested them. They've been unassigned since the beginning and likely always will be.

Could Something Be Using It?

Technically, yes. There are no unassigned port police. Any application could listen on port 340 for private or unofficial purposes:

• Internal corporate protocols
• Custom services in isolated networks
• Research projects
• Malware (any port can be exploited)

But there's no common unofficial use that's widely documented. Port 340 isn't like port 8080 (unofficial HTTP alternative) or port 31337 (historically associated with exploits). It's just... unused.

Checking What's Listening

On Unix-like systems:

# See if anything is listening on port 340
sudo lsof -i :340
sudo netstat -tulpn | grep :340

On Windows:

netstat -ano | findstr :340

If nothing returns, nothing's using it. Which is the expected result.

The Honest Reality

Most ports tell a story. Port 340 doesn't. It's a number in a registry that no one ever needed. After forty years of Internet history, that's unlikely to change.

Not every port needs to carry traffic. Some just exist as gaps in the sequence—numbers that were allocated in case they'd be useful, and never were.

Port 340 is one of those numbers. And that's fine.

Related Ports

• Ports 334-343 — The full unassigned block that includes port 340
• Port 344 — PDAP (Prospero Data Access Protocol)—the first assigned port after this unassigned range
• Port 333 — Texar Security Port—the assigned port immediately before this unassigned range