Port 176 is officially assigned to GENRAD-MUX, a multiplexing protocol developed for General Radio Company's automated test equipment.12 This is one of those ports that captures a specific moment in industrial automation history—when test equipment manufacturers were figuring out how to make their instruments talk to computers over networks.
What GENRAD-MUX Does
GENRAD-MUX was designed to allow General Radio's test and measurement equipment to communicate with computer systems over a network. The protocol handled multiplexed connections between automated test systems and various measurement instruments—oscilloscopes, multimeters, signal generators, and other test equipment that needed computer control.3
Think of it as an early industrial IoT protocol, long before anyone called it that. In the 1980s, as factories and test labs started automating their measurement processes, someone at General Radio had to solve the problem: "How do we make twenty different instruments all talk to one computer without a rat's nest of cables?"
Their answer was GENRAD-MUX on port 176.
General Radio Company
General Radio Company (later GenRad) was founded in 1915 and spent decades as a leading manufacturer of precision test and measurement equipment.4 By the time computer-controlled testing became viable in the 1970s and 1980s, GenRad had extensive product lines: impedance meters, sound level meters, frequency standards, RLC bridges, and automated test equipment for circuit boards.5
The company was developing automated test programs as early as 1982.6 This was the era when every equipment manufacturer created their own proprietary protocols for instrument control—GPIB (IEEE-488) was emerging as a standard, but networked test equipment was still the Wild West.
GenRad was eventually acquired by Teradyne in 2001, and the product line later moved to IET Labs.7 The GENRAD-MUX protocol represents a path not taken—a proprietary solution from when the industry hadn't yet converged on standard approaches.
The Reality of Port 176 Today
Port 176 is rarely seen in modern networks. The protocol it was designed for served a specific ecosystem of test equipment that has largely been retired or replaced. Modern test equipment uses standardized protocols like SCPI over TCP/IP, VXI-11, or LXI standards.
You might encounter port 176 in:
- Legacy test labs with vintage GenRad equipment still in operation
- Industrial facilities with decades-old automated test systems
- Museums of computing and measurement history
But mostly, you won't encounter it at all.
Well-Known Port Range
Port 176 sits in the well-known port range (0-1023), which is reserved for system services and historically significant protocols assigned by IANA (Internet Assigned Numbers Authority). These assignments were made when the port space was being carved up in the early days of TCP/IP networking.8
Getting a well-known port assignment meant your protocol was considered important enough to deserve permanent reservation. GENRAD-MUX received this designation when networked test equipment automation was a cutting-edge industrial capability.
Why This Port Matters
Port 176 is a time capsule. It represents an era when:
- Every major equipment manufacturer was inventing their own networking protocols
- Industrial automation was moving from hardwired control to networked systems
- The Internet protocol suite was being applied to problems beyond email and file transfer
- Nobody knew which approaches would become standards and which would become museum pieces
The port exists because test engineers needed their instruments to talk to their computers, and General Radio built a solution. That solution got a port number. The equipment moved on. The port number remains.
Checking Port 176
To see if anything is listening on port 176 on your system:
On Linux or macOS:
On Windows:
If you find something listening on port 176 and you're not running vintage test equipment, investigate carefully. Old assigned ports sometimes get repurposed by malware precisely because they're expected to be dormant.
The Unassigned Question
Interestingly, some sources list port 176 as "unassigned" while the official IANA registry shows it assigned to GENRAD-MUX.1 This discrepancy itself tells a story: when a protocol becomes obscure enough, even its port assignment starts to fade from collective memory.
This is what happens to protocols that don't achieve widespread adoption. They get assigned, they serve their purpose in a specific ecosystem, and then they quietly fade while their port number remains reserved—a fossil in the registry.
Related Ports
Port 176 stands somewhat alone in the port registry, without obvious siblings or related services nearby. This isolation makes sense: it was a proprietary solution for a specific product line, not part of a larger protocol family that would have claimed multiple sequential ports.
Was this page helpful?