Port 3210: Registered, Obscure, and Quietly Occupied

What Range This Port Belongs To

Port 3210 sits in the registered ports range (1024–49151). These ports require IANA registration, which means a company or individual formally applied and was assigned the port. Unlike the well-known ports below 1024, registered ports don't require root privileges to open — and unlike the ephemeral ports above 49151, they're supposed to have a stable, declared purpose.

"Supposed to" is doing a lot of work in that sentence.

The Official Owner

IANA's registry lists port 3210 as belonging to "flamenco-proxy" — described as "Flamenco Networks Proxy," assigned to one Corey Corrick, on both TCP and UDP.¹

Flamenco Networks was a networking company that appears to have built some form of HTTP proxy infrastructure. Beyond that, the trail goes cold. The company left almost no footprint on the modern web. The port assignment remains, frozen in the registry like an insect in amber — official, valid, and functionally meaningless.

This is not unusual. The registered port range contains hundreds of assignments to products that were discontinued, companies that folded, or projects that never shipped. The registry is a historical record as much as a practical one.

Who Actually Uses It

Convex, a modern backend-as-a-service platform, uses port 3210 as the default port for its local development backend.² When you run Convex locally, it starts its backend service on this port. Developers building with Convex see it constantly in their local environments.

Convex didn't announce this choice or formally claim the port — they simply picked it, possibly because it was uncontested in practice. Port 3210 also has a historical footnote as a UDP port used by the PC game Faces of War.³

None of these uses conflict in practice. Flamenco Networks isn't running. Faces of War servers aren't competing with your local Convex instance.

Why Unassigned-in-Practice Ports Matter

The registered port space is 48,128 ports wide. IANA has assigned many of them. A significant number of those assignments point to things that no longer exist — products discontinued, companies dissolved, protocols abandoned.

This creates a quiet gray zone: ports that are technically "taken" but practically available. Developers and tools fill the vacuum, picking numbers that feel unclaimed because nothing is actively using them. Port 3210 is a small example of how the Internet's namespace actually evolves — not through formal reassignment, but through gradual, informal drift.

If you see port 3210 open on a machine, the most likely explanation is a Convex local backend. Less likely but possible: someone configured a proxy or custom service there. The Flamenco Networks explanation belongs to history.

How to Check What's Listening

# On macOS/Linux
sudo lsof -i :3210

# Or with netstat
netstat -an | grep 3210

# On Windows
netstat -aon | findstr :3210
# Then look up the PID: tasklist | findstr <PID>

If something's listening on port 3210 on your machine and you didn't expect it, those commands will tell you the process. Nine times out of ten on a developer machine, it's Convex.