What Runs on This Port
Port 211 is officially assigned to 914c-g, the service name for the Texas Instruments 914C/G Terminal.1 Both TCP and UDP protocols can use this port. The assignment was registered by Bill Harrell sometime in the early Internet era, when manufacturers routinely registered dedicated ports for their specific hardware.
The Texas Instruments 914 series were video terminals from the 1970s—business-grade machines with 2260 and 3270 emulation modes that cost $3,200 in 1975 dollars.2 These terminals connected to mainframes and minicomputers in corporate data centers, and this port facilitated that communication.
The Well-Known Ports Range
Port 211 sits in the well-known ports range (0-1023), sometimes called system ports. IANA manages these assignments, and they were historically reserved for specific services and protocols. In the early days of the Internet, this made sense: assign each service a number, maintain the registry, prevent collisions.
What happens when the hardware dies but the port number lives on? Port 211 happens.
The Name Change Nobody Noticed
IANA originally registered this port as "914c/g"—with a slash character. At some point, they realized that slash-based service names don't work well with modern service discovery mechanisms. So they created the "well-formed" replacement name: "914c-g" with a hyphen.1
The original "914c/g" is now officially historic—deprecated in IANA's database. They renamed a service for hardware that probably hasn't powered on since the Reagan administration.
What Actually Uses This Port
Realistically? Nothing. The Texas Instruments 914C/G terminals are museum pieces if they exist at all. You will not find this protocol running in any modern network.
Port 211 has occasionally appeared in security advisories—malware sometimes uses obscure assigned ports like this one because administrators don't monitor them closely.3 An old Trojan used port 211 for command and control communication. The port wasn't vulnerable; it was just available and unlikely to be watched.
Why This Port Matters
Port 211 represents what happens to infrastructure over time. The Internet's port registry contains hundreds of assignments like this—specific hardware, defunct protocols, companies that no longer exist. IANA doesn't routinely reclaim these assignments. Once a port is registered, it tends to stay registered.
This creates a curious archaeology. You can read through IANA's port list and find Digital Equipment Corporation protocols, services for long-dead Unix variants, and terminal servers for hardware that was obsolete before the Web existed.
Port 211 is a gravestone with a number on it.
How to Check What's Listening
If you want to see whether anything is actually using port 211 on your system:
On Linux or Mac:
On Windows:
If something is listening on port 211, it's not the Texas Instruments terminal protocol. It's either custom software that chose this port arbitrarily, or something you should investigate.
The Lesson
Port 211 teaches you something about how the Internet works: we build on top of layers we never clean up. The port registry is full of ghosts. Services that made sense in 1982. Hardware that no company manufactures anymore. Protocols that no software implements.
But the numbers remain assigned, reserved, waiting for traffic that will never come.
Port 211 is still there. The terminal is not.
Related Ports
- Port 23 — Telnet, another obsolete protocol for terminal access (though far more widely used in its time)
- Port 22 — SSH, the secure replacement for terminal protocols like Telnet
- Port 513-514 — Remote login services (rlogin, rsh) from the same era
Frequently Asked Questions
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