Port 1112 is officially registered with IANA for the "Intelligent Communication Protocol" (ICP) on both TCP and UDP. That's the official story. The real story is that nobody knows what the Intelligent Communication Protocol actually does.
What Runs on This Port
Official assignment: Intelligent Communication Protocol (ICP) Actual use: ESET antivirus updates, mini-SQL database servers, and whatever else needed a port number
Port 1112 sits in the registered ports range (1024-49151), where organizations can request IANA to assign them a specific port for their protocol or service. Someone requested 1112 for the Intelligent Communication Protocol. IANA approved it. And then... nothing.
The Protocol That Isn't There
Search for documentation about the Intelligent Communication Protocol. You won't find an RFC. You won't find implementation guides. You won't find a community of users discussing it on forums or Stack Overflow. You'll find the name in port databases and nothing else.
This happens more often than you'd think. The port registry is full of ghosts—protocols that were registered decades ago, used briefly or never at all, and now exist only as entries in a database. The name suggests something important: "Intelligent Communication Protocol." But intelligence requires presence, and this protocol has none.
What Actually Uses Port 1112
Nature abhors a vacuum. So does networking.
When a registered port sits empty, other software moves in:
ESET antivirus uses TCP port 1112 for virus definition updates. Not because ESET has anything to do with the Intelligent Communication Protocol, but because they needed a port and this one was available.1
Mini-SQL servers sometimes listen on port 1112. Mini-SQL (mSQL) is a lightweight database server from the 1990s. It needed a port. Port 1112 was sitting there unused.1
These are unofficial uses—software that looked at the port list, saw 1112 wasn't being actively used for its registered purpose, and claimed it. This is how ports actually work in practice. The registry is a suggestion. Reality is whatever's listening.
The Registered Ports Range
Port 1112 belongs to the registered ports range: 1024 through 49151.
These ports are assigned by IANA to specific services, but the assignments aren't enforced. You can run whatever you want on port 1112. The operating system doesn't check whether you're actually running the Intelligent Communication Protocol before letting you bind to this port. The registration is documentation, not law.
Well-known ports (0-1023) require root privileges to bind on Unix systems, which provides some protection against random software claiming port 22 or 80. Registered ports have no such protection. If your software wants to listen on 1112, it can. If ESET and mini-SQL both try to use 1112 on the same machine, one of them will fail to start, and you'll get a "port already in use" error.
How to Check What's Listening on Port 1112
On Linux or macOS:
On Windows:
These commands show you what process (if any) is actually listening on port 1112 on your machine. You might find ESET. You might find a database server. You might find nothing at all.
If you find something unexpected, investigate it. Port 1112 isn't commonly used by malware, but any port can be. Check what process owns it. If you don't recognize the software, find out what it is.
Why Unassigned (or Barely Assigned) Ports Matter
The port registry exists to prevent conflicts. If everyone who needed a port just picked a random number, we'd have chaos—software constantly colliding, unable to communicate because two different protocols claimed the same port.
IANA's registry solves this through coordination. Organizations request ports. IANA assigns them. Everyone checks the registry before picking a port number. In theory.
In practice, many registered ports are like 1112—claimed but not used, or used for purposes completely different from their registration. The registry is a map of intentions, not reality. The real question is always: what's actually listening?
The Intelligent Communication Protocol Mystery
Here's what we know about the Intelligent Communication Protocol:
- It exists in the IANA registry
- It was assigned port 1112 for both TCP and UDP
- Someone registered it at some point
Here's what we don't know:
- What it does
- Who created it
- Whether it was ever implemented
- Why it was called "intelligent"
This is the ghost in the registry. A name without a body. A port assignment without traffic. A protocol that might have mattered once, or might have never existed at all beyond the registration form.
And yet port 1112 still serves a purpose. It's a number that software can use when they need one. ESET updates your antivirus definitions. Mini-SQL serves database queries. The Intelligent Communication Protocol might be absent, but the port itself is very much alive.
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