Port 378 sits in the well-known ports range (0-1023), officially assigned but functionally forgotten. It belongs to NEC Corporation's dsETOS service, a protocol from the early 1990s that has left almost no trace in modern networking.
What dsETOS Was
The IANA registry lists port 378 for "dsETOS" on both TCP and UDP, with Tomoo Fujita at NEC Corporation as the contact.1 The assignment appears in RFC 1700 from October 1994, the last comprehensive snapshot of assigned numbers before the registry moved online.2
The "ds" prefix suggests "data service" or "distributed service." Port 377 is assigned to "tnETOS," also from NEC, hinting at a related suite of protocols. But beyond these registry entries, dsETOS has vanished. No public protocol specifications. No user communities. No modern implementations.
The Well-Known Ports Range
Port 378 occupies valuable real estate. Well-known ports (0-1023) require root privileges to bind on Unix systems and are assigned by IETF Review or IESG Approval—the highest bar for port allocation.3 These ports were meant for fundamental Internet services.
Most well-known ports earned their place: SSH on 22, DNS on 53, HTTPS on 443. Port 378 earned its place in 1994 when the Internet was smaller and the future less certain. NEC was a major technology company. The protocol might have mattered.
It didn't.
What Actually Uses This Port
In practice, port 378 is essentially unused. Security scanning databases note it exists.4 Port scanning tools will check it. But you won't find active services listening here.
Some security sources mention that malware has occasionally used port 378 for command and control, precisely because it's assigned but unused—a quiet corner where unexpected traffic might go unnoticed.5 This is the fate of abandoned ports: squatters move in.
Why Keep It?
The IANA registry is forever. Once a port is assigned, it stays assigned. Removing an allocation could break something, somewhere, even decades later. Maybe an industrial system in a Japanese factory still runs dsETOS. Maybe Tomoo Fujita's email address still works and he occasionally receives queries.
Or maybe not. But the registry doesn't care. Port 378 remains assigned to dsETOS, a monument to a protocol that history forgot.
Checking Port 378
To see if anything is listening on port 378 on your system:
Linux/Mac:
Windows:
You'll almost certainly find nothing. That's normal. Port 378 is a ghost.
The Archaeology of the Internet
Every abandoned port tells a story about what the Internet was and what it might have become. Someone at NEC designed dsETOS. Someone at IANA approved the allocation. Someone thought this protocol would matter enough to occupy a well-known port forever.
They were wrong, but the port remains. The registry is the Internet's Akashic Record—nothing is deleted, everything is remembered, even when nobody knows why anymore.
Port 378 is officially assigned, properly registered, and utterly forgotten. This is what a ghost port looks like.
Related Ports
- Port 377 (tnETOS): The sibling protocol, also from NEC Corporation, equally obscure
- Ports 0-1023: The well-known ports range, requiring elevated privileges to bind
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