Port 2445: DTN1 — Reserved, Rarely Seen

Port 2445 is a registered port — assigned by IANA in the range between 1024 and 49151 where services stake their claims. Some sources list it under the name DTN1, a reference to early experimentation with delay-tolerant networking. In practice, this port sits empty on nearly every system you'll encounter.

The Registered Range

Ports 1024 through 49151 are called registered ports. Unlike the well-known ports below 1024 (HTTP, SSH, DNS — the foundational services), registered ports don't require elevated privileges to bind. Any user-level process can open them.

IANA maintains a registry of assignments in this range — organizations and projects can apply to claim a port number for their protocol. The idea is coordination: if two applications both want port 2445, chaos ensues. Registration prevents that, in theory.

The catch: registration doesn't mean deployment. A protocol can reserve a port, publish an RFC, and then fail to achieve adoption. The port number sits claimed on paper while remaining empty in practice.¹

The DTN1 Connection

Some port databases list port 2445 as assigned to DTN1 — an early variant of the Bundle Protocol used in delay-tolerant networking (DTN). DTN was designed for environments where connections are intermittent, latency is extreme, or links break constantly: deep space probes, disaster zones, remote sensors.

The deeper DTN work eventually settled on port 4556 for the TCP convergence-layer protocol (the mechanism that lets DTN nodes communicate over standard TCP links).² Port 2445 appears to be an earlier or alternate registration that predates that standardization.

If DTN1 on port 2445 ever saw real deployment, evidence of it is scarce. This is honest — not a failure of research. Some ports just don't make it.

Security Databases and Malware Flags

A handful of security scanners flag port 2445 as having been associated with malicious software at some point in its history.³ This is worth understanding without over-weighting.

Security databases sometimes flag a port when malware is observed using it — even opportunistically, even once. Malware authors pick ports partly to blend in and partly at random. A flag in a security database doesn't mean this port belongs to malware; it means someone's tooling used it at some point.

The honest read: there's no well-known malware family that calls port 2445 home. If you see unexpected traffic on this port, investigate. If you see nothing, that's normal.

What's Actually Listening on Your System

To check whether anything is using port 2445 on your machine:

macOS / Linux:

# Show what process is listening on port 2445
sudo lsof -i :2445

# Or with ss (Linux):
ss -tlnp | grep 2445

# Or with netstat:
netstat -tlnp | grep 2445

Windows:

netstat -ano | findstr :2445

On a typical system, you'll get no output. That's the expected result.

Why Unassigned Ports Matter

The port number space isn't infinite — there are 65,535 of them. The registered range is the middle third, where legitimate services compete for addresses. Keeping this space organized matters because:

• Firewall rules reference port numbers. Ambiguous assignments create security uncertainty.
• Network monitoring tools flag unexpected ports. Known assignments reduce false positives.
• Application developers need to pick ports that won't collide with other services on the same host.

Port 2445 represents the quiet majority of the registry: assigned, technically valid, practically invisible. The Internet is built on a handful of ports that everyone uses, surrounded by thousands of ports reserved for protocols the world hasn't needed yet — or tried and moved on from.