Port 3423: Unassigned — Registered Range, No Official Tenant

What Range This Port Belongs To

Port 3423 falls in the registered port range (1024–49151), also called user ports. This is the middle tier of the port numbering system:

• Well-known ports (0–1023): Assigned to foundational protocols — HTTP, SSH, DNS, SMTP. Require root privileges to bind on Unix systems.
• Registered ports (1024–49151): Organizations and vendors register these with IANA for specific applications. No root required to bind.
• Dynamic/ephemeral ports (49152–65535): Unregistered. Used temporarily by operating systems for outbound connections.

The registered range is vast — over 48,000 ports — and IANA maintains the official registry. Port 3423 appears in that registry as unassigned: no service name, no protocol, no RFC. The slot is empty.

Observed Unofficial Uses

Several informal port databases list port 3423 as associated with the Xware xTrm Communication Protocol — a proprietary messaging protocol reportedly used in industrial automation and logistics systems (SCADA platforms, warehouse management, manufacturing control).¹

These sources describe it as TCP-based, designed for real-time data exchange between sensors, control systems, and enterprise software. Security researchers have noted it lacks built-in encryption.

However, this documentation appears to be informal — the protocol was never officially registered with IANA. What likely happened: some vendor used this port for an internal protocol, it got catalogued by one port database, and that entry propagated through the ecosystem. This is common. Port databases cite each other more than they cite IANA.

Bottom line: If you see traffic on port 3423, it is probably either:

• A legitimate application that chose this port arbitrarily
• Industrial automation software using Xware or similar tooling
• Something else entirely — there is no official service to expect here

How to Check What Is Listening

On Linux/macOS:

# Show which process is bound to port 3423
ss -tlnp | grep 3423

# Or with netstat
netstat -tlnp | grep 3423

# Or with lsof
lsof -i :3423

On Windows:

netstat -ano | findstr :3423

The output will show you the process ID (PID). Match that to a process name with Task Manager or tasklist /fi "PID eq <pid>".

With nmap (scanning a remote host):

nmap -sV -p 3423 <target>

The -sV flag attempts service detection — it will probe the port and try to identify what is actually running, regardless of what any database says should be there.

Why Unassigned Ports Matter

The port numbering system only works if applications agree on which door to knock on. A web browser knows to connect to port 443 for HTTPS because that assignment is official, documented, and universally respected.

Unassigned ports like 3423 exist in a gray zone. Any application can claim them — and many do, without registering. This creates predictable problems:

• Conflicts: Two applications on the same machine want the same unassigned port. One loses.
• Firewall ambiguity: Network administrators cannot make informed decisions about blocking or allowing traffic they cannot identify.
• Security gaps: Malware occasionally uses obscure registered ports knowing that security tools may not inspect traffic there carefully.

The registered range exists precisely to prevent this chaos. That only works when vendors actually register. Port 3423 is a small example of the gap between how the system is supposed to work and how it actually does.