What Port 2563 Is
Port 2563 sits in the registered ports range (1024–49151). These ports aren't free-for-all like the ephemeral ports above 49151, but they're also not guarded like the well-known ports below 1024. Anyone can request a registration from IANA, and IANA will assign it — no proof of a working protocol required.
Port 2563 was registered to CTI Redwood, with a contact listed as Songwon Chi at daou.co.kr — the domain of Daou Systems, a Korean IT company.1 CTI stands for Computer Telephony Integration, a category of software that bridges phone systems and computers. Beyond that, public documentation about what "CTI Redwood" actually does as a protocol is essentially nonexistent.
This makes port 2563 a ghost port: officially assigned, technically claimed, but functionally inert on the public Internet.
What Ghost Ports Tell Us
The IANA registry contains thousands of entries like this one. A company registers a port for an internal product, the product ships (or doesn't), and the registration outlives any public use by decades. The port sits in the registry forever — IANA doesn't reclaim registrations — while the rest of the Internet routes around it.
This isn't a flaw. The registered ports range exists precisely to let organizations claim space without having to publish an open standard. The cost is a registry full of fossils.
Security Note
An unrecognized service on port 2563 on your network is worth investigating. Because this port has no well-known legitimate use, anything listening on it is either:
- A proprietary CTI application from Daou Systems or similar Korean enterprise software
- A misconfigured service that landed here accidentally
- Something you should look at more carefully
How to Check What's Listening
macOS / Linux:
Windows:
Cross-platform (nmap):
If something is listening on this port and you don't know what it is, lsof on Unix will show you the process name and PID. From there, you can trace it to the executable.
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