Port 3243: Timelot — The Port That Got Named and Forgotten

Port 3243 sits in the registered port range and carries an official IANA name — "timelot" — assigned in February 2002. That's nearly everything that's publicly documented about it.

The Registered Port Range

Ports 1024 through 49151 are registered ports. Unlike the well-known ports below 1024 (which require root privileges to bind on Unix systems and carry familiar protocols like HTTP, SSH, and DNS), registered ports can be claimed by applications and services through IANA without the same level of scrutiny or standardization.

The practical result: thousands of ports in this range carry names that once meant something to someone, filed and then never widely documented or adopted.

Port 3243 is one of them.

Timelot

The IANA registration reads: timelot — Timelot Port — TCP and UDP — registered February 2002.¹

No RFC was published. No protocol specification appears in public archives. The name suggests something related to time slots or scheduling, but what company or developer filed the registration, and what became of the product, isn't publicly documented. If Timelot ever shipped, it didn't leave much of a footprint.

Network administrators have occasionally flagged unexpected traffic on port 3243 in security forums, confused that a recognized IANA name produces no useful results when researched. That's the uncomfortable middle ground: officially registered, effectively unknown.

Citrix Framehawk (Range Overlap)

One real-world source of port 3243 traffic: Citrix NetScaler Gateway, which used ports 3224 through 3324 for its Framehawk protocol — a UDP-based display remoting technology designed for high-latency, lossy network conditions.² If you're seeing port 3243 traffic in a Citrix environment, Framehawk is a plausible explanation. Citrix has since replaced Framehawk with EDT (Enlightened Data Transport), so this usage is increasingly historical.

How to Check What's Listening

If port 3243 shows up on your network, find the process:

macOS / Linux:

sudo lsof -i :3243
sudo ss -tulpn | grep 3243

Windows:

netstat -ano | findstr :3243
# Then look up the PID:
tasklist | findstr <PID>

All platforms — open connection check:

nmap -sV -p 3243 <target>

The process name will tell you more than the port number ever could.

Why This Port Exists

Registered ports like 3243 are a snapshot of software history. A developer or company files a registration, ships a product (or doesn't), and the port number persists in IANA's registry indefinitely. Some of these registrations represent thriving protocols. Others are tombstones — names attached to software that never shipped, or shipped and disappeared.

Port 3243 appears to be the latter. It has a name. It just doesn't have a story that survived.