Port 3425: AGPS Access Port — Assigned but Absent

Port 3425 sits in the registered port range with an IANA name: agps-port, assigned for "AGPS Access Port." AGPS is Assisted GPS — a system that helps GPS receivers get a faster location fix by downloading satellite almanac and ephemeris data over a network connection instead of waiting for the slow satellite signal to deliver it.¹

The concept is real and widely used. When your phone gets a GPS fix in seconds instead of minutes, that's A-GPS at work.² But the specific implementation that was supposed to use port 3425 never materialized into anything documented or deployed. There's no RFC. There's no protocol specification. There's no known software that opens this port for AGPS service.

IANA assigned the name, but nothing moved in.

What Range This Port Belongs To

Port 3425 falls in the registered port range (1024–49151), also called User Ports. IANA manages this range on a first-come, first-served basis — organizations and developers can request an assignment for a service they intend to build. The bar for registration is lower than for well-known ports (0–1023), which is why the range contains thousands of entries ranging from critical infrastructure to optimistic reservations for software that was never finished.³

An IANA entry is a name, not a promise. It means someone submitted a request. It doesn't mean the protocol was ever implemented, standardized, or deployed anywhere.

What You'll Actually Find on Port 3425

Almost certainly nothing. If you scan the open Internet for port 3425, you're unlikely to find legitimate services. You might find:

• Misconfigured services — an admin who picked this port because it seemed unused
• Malware or backdoors — attackers sometimes use obscure registered ports to blend into noise
• Nothing at all — the most common result

How to Check What's Listening

If port 3425 is open on a machine you're investigating:

Linux / macOS:

# Show the process using port 3425
lsof -i :3425

# Or with ss (modern Linux)
ss -tlnp sport = :3425

Windows:

netstat -ano | findstr :3425

Then match the PID to a process in Task Manager or:

tasklist /FI "PID eq <pid>"

If something is listening on port 3425 and you don't recognize it, that's worth investigating. The port has no established legitimate software using it.

Why Unassigned Ports Matter

The registered port range exists as a coordination mechanism — a way to reduce the chance that two different applications accidentally pick the same port number and conflict. When developers need a well-known port for their software, they register it so the community knows where to find it.

But the system only works when registrations reflect real deployments. Port 3425's agps-port entry is the kind of ghost that accumulates over decades: a name without a protocol, a reservation for infrastructure that found another way to be built. AGPS traffic today typically runs over port 7275 (for SUPL — Secure User Plane Location), not port 3425.⁴

Port 3425 is a reminder that the port registry is part history, part aspiration, and only partially a map of what's actually running on the Internet.