Port 2235: Sercomm-WLink — Registered, Unknown, Quiet

What Range This Port Belongs To

Port 2235 sits in the registered ports range (1024–49151). This range is managed by IANA — the Internet Assigned Numbers Authority, the organization responsible for coordinating global IP address space and protocol registries. Any company or individual can apply to register a port in this range, which distinguishes it from the well-known ports (0–1023) that require stricter justification.

Registered ports don't carry the same authority as well-known ports. Port 80 being HTTP is a hard fact of the Internet. Port 2235 being Sercomm-WLink is a soft registration: it means someone asked IANA to reserve it, IANA said yes, and everyone else agreed to avoid it.

The Official Registration

IANA's registry assigns port 2235 (both TCP and UDP) to Sercomm-WLink, a protocol from Sercomm, a Taiwanese manufacturer of networking hardware — routers, modems, and broadband equipment — primarily built for ISPs and carriers.¹

The registration contact is listed as Melinda Tsao. No RFC was ever published. No public specification exists. This is a proprietary protocol, registered to prevent collision, not to become an Internet standard.

What Sercomm-WLink actually does at the protocol level isn't publicly documented. Based on Sercomm's product line, it likely relates to device management or configuration communication between Sercomm hardware and management systems — the kind of internal traffic that flows between a router and its controller and never needs to leave the manufacturer's ecosystem.

Who You'll Find Here in Practice

Almost no one. Port 2235 is quiet on the open Internet. Sercomm equipment exists primarily in ISP-managed networks behind closed doors. If you see traffic on port 2235 in a consumer or enterprise environment, it isn't Sercomm-WLink. It's either:

• A custom application that chose this port because it appeared unoccupied
• Malware probing or communicating (port 2235 has appeared on historical malware port lists, though it's not associated with any specific family)
• A misconfigured service

How to Check What's Listening

If you see activity on port 2235 and want to know the source, these commands will tell you:

macOS / Linux:

# Show which process is listening on port 2235
sudo lsof -i :2235

# Or with ss (Linux):
sudo ss -tlnp | grep 2235

Windows:

netstat -ano | findstr :2235

The output will give you a process ID. Cross-reference it with Task Manager (Windows) or ps aux (macOS/Linux) to identify the application.

Why Unassigned-in-Practice Ports Matter

IANA's registered port range contains thousands of ports like this one: technically assigned, practically empty. They serve a real function in the ecosystem — they're claimed land. By registering port 2235, Sercomm established that legitimate Sercomm-WLink traffic belongs here, which means network administrators and firewall vendors know that unexpected traffic on this port is worth investigating.

The alternative — a completely unclaimed port — offers no signal at all. A registered but quiet port is, in a small way, a useful data point: something out of the ordinary is worth a second look.