Port 3174: ARMI Server — A Name Without a Story

What Port 3174 Is

Port 3174 sits in the registered port range (1024–49151). These ports are managed by IANA, which assigns names to them when organizations submit a request. Unlike well-known ports (0–1023), registered ports don't require elevated privileges to open, and their assigned services range from widely deployed protocols to obscure internal systems that never saw broad adoption.

IANA lists port 3174 as "ARMI Server" on both TCP and UDP.¹ That name appears in the official registry and almost nowhere else. No RFC defines the protocol. No major software documentation references it. The registration exists, and the story behind it largely doesn't.

The Gaming Footnote

Port 3174 is more recognizable in gaming circles than in any server room. Tom Clancy's Rainbow Six: Vegas and Rainbow Six: Vegas 2 used the UDP range 3074–3174 for multiplayer traffic.² Port 3174 is simply the top of that range — not special in itself, just where the range ended.

If you ever opened your router's port forwarding settings to get co-op working in Vegas, you touched this port.

What's Actually Listening on This Port

On any given machine, port 3174 is almost certainly not doing anything — unless you're running software that specifically claimed it. To check:

macOS / Linux:

sudo lsof -i :3174

Windows (Command Prompt):

netstat -ano | findstr :3174

If nothing comes back, the port is closed. If something does, the process ID in the output will tell you what's using it.

Why Unassigned (or Lightly Assigned) Ports Matter

The registered port range contains thousands of entries like this one — names without living protocols, registrations from projects that never shipped or services that silently faded. They matter for a few reasons:

Firewall rules need to account for them. An attacker or piece of malware can bind to any registered port. A port having a name doesn't mean only legitimate traffic will use it.

Port scanners flag them. If a security scan shows something listening on 3174, the IANA name "ARMI Server" won't explain it. You still need to identify the actual process.

The range itself is finite. IANA stopped accepting new registrations for ports that aren't actively maintained. The registered range is filling up with history as much as with current use.

Port 3174 is what most of the port registry quietly is: a placeholder for something that made sense to someone, once, and now just holds the number.