Port 392 carries the designation "synotics-broker" in the IANA registry. Both TCP and UDP. Officially assigned to the SynOptics Port Broker Port service.
Here's what makes it strange: SynOptics Communications hasn't existed since 1994.
What SynOptics Was
SynOptics Communications was founded in 1985 by Andrew Ludwick and Ronald Schmidt, both refugees from Xerox PARC. They built the company that popularized the Ethernet hub — those blinking boxes that turned single network cables into many.1
They were fast. In six years (1986-1992), revenue went from $1.8 million to $388 million. They became the market leader in Ethernet LAN hubs, beating 3Com and Cabletron.2
They needed ways to manage all those hubs. Port 391 was their SNMP relay. Port 392 was their Port Broker. Port 412 was their trap convention port. Three ports for three pieces of network management infrastructure that helped administrators keep the hub networks running.
The Merger That Ended SynOptics
On July 6, 1994, SynOptics merged with Wellfleet Communications to form Bay Networks.3 Bay Networks itself was later acquired by Nortel in 1998. Nortel collapsed spectacularly in the early 2000s.
Port 392 remains. The company is gone. The protocol is obsolete. The hubs have been replaced by switches, then by software-defined networks, then by cloud infrastructure where physical topology barely matters.
But the port assignment is permanent.
What This Port Tells You About the Registry
The well-known port range (0-1023) is full of these fossils. Companies that no longer exist. Protocols that no one uses. Services that solved problems we don't have anymore.
IANA doesn't revoke port assignments. Once a port is assigned, it stays assigned. This creates a permanent archaeological record of networking history, frozen in the registry like insects in amber.
If you scan port 392 on a modern network, you will almost certainly find nothing. The SynOptics Port Broker service isn't running anywhere. The code probably doesn't exist. The engineers who wrote it have moved on.
How to Check What's Listening
If you want to verify nothing is using port 392 on your system:
Linux/Mac:
Windows:
If something responds, it's not the SynOptics Port Broker. It's something else that chose to use an assigned-but-abandoned port.
Why Unassigned Ports Matter Less Than You Think
People worry about the well-known port range filling up. "What happens when we run out of ports 0-1023?"
We already ran out. That's why the registered port range (1024-49151) exists. And the dynamic/ephemeral range (49152-65535) for temporary connections.
Port 392 shows you the truth: most well-known ports aren't well-known anymore. They're historical markers. The Internet routes around them.
The Port Broker port did its job in the 1990s. SynOptics hubs managed networks that connected the early commercial Internet. Those networks are gone. The port remains. That's the deal.
Related Ports
- Port 391 — SynOptics SNMP Relay Port
- Port 412 — SynOptics Trap Convention Port
- Port 161 — SNMP (the standard that replaced vendor-specific management protocols)
Frequently Asked Questions
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