Port 1107: ISOIPSIGPORT-2 — The registered port nobody remembers

Port 1107 sits in that strange middle ground of the Internet's port system—officially registered, technically assigned, practically forgotten.

What Port 1107 Is Registered For

According to IANA's official registry, port 1107 is assigned to ISOIPSIGPORT-2 for both TCP and UDP.¹ The name suggests something related to ISO IP signaling (International Organization for Standardization Internet Protocol signaling), likely a secondary signaling port in some protocol suite that also uses port 1106 (ISOIPSIGPORT-1).

But that's where the trail goes cold. There's no RFC documenting it. No widely-used software announces it runs on this port. No security advisories warn about exploits targeting it. The protocol exists in the registry and almost nowhere else.

The Registered Ports Range

Port 1107 belongs to the registered ports range (1024-49151). This is the middle tier of the port number system:

• Well-known ports (0-1023): Reserved for common services like HTTP, SSH, and DNS. Require root/admin privileges to bind on Unix-like systems.
• Registered ports (1024-49151): Available for registration with IANA for specific services. This is where port 1107 lives—officially claimed but not necessarily actively used.
• Dynamic/ephemeral ports (49152-65535): Not assigned to any service. Used temporarily by client applications when establishing outbound connections.

Registered ports represent the Internet's middle class—they have official assignments, but many of them are legacy protocols, abandoned projects, or services that never gained widespread adoption.²

What Might Be Using Port 1107

The honest answer: probably nothing.

Some possibilities:

• Legacy ISO protocol infrastructure that never achieved widespread deployment
• Proprietary software that happened to use this registered port number
• Nothing at all on most systems—this port likely sits closed and unused

The port exists as a reservation, a placeholder in the global registry. But unlike HTTP on port 80 or SSH on port 22, there's no thriving ecosystem built around it.

Checking What's Listening on Port 1107

If you're curious whether anything is actually using port 1107 on your system:

On Linux or macOS:

# Check for listening services
sudo lsof -i :1107

# Or using netstat
sudo netstat -tuln | grep 1107

# Or using ss (modern alternative)
sudo ss -tuln | grep 1107

On Windows:

# Check for listening services
netstat -an | findstr :1107

If nothing returns, the port is closed—which is the expected state for most systems.

Why Obscure Ports Matter

Port 1107 might seem pointless—an assigned number for a protocol nobody uses. But these obscure registered ports tell a story about how the Internet evolved.

Every registered port represents a moment when someone thought their protocol would matter. Someone filled out the IANA paperwork. Someone believed this service would need a permanent address on the Internet's nervous system.

Most of those predictions didn't pan out. The Internet is littered with abandoned ports, forgotten protocols, and services that never found their audience. But the registrations remain, fossil records of things that almost were.

And occasionally, one of these sleeping ports wakes up. A new application needs a port number and picks one from the registered range. An old protocol gets revived. The door that's been closed for decades suddenly opens.

Port 1107 is probably closed on your machine right now. But it's there, waiting, officially registered and ready if something ever needs it again.

Security Considerations

The obscurity of port 1107 means:

• Low attack surface: It's unlikely to be targeted by automated scans looking for common vulnerabilities, since there's no well-known service to exploit.
• But if something is listening: Any service running on this port is non-standard and worth investigating. Check what process owns it and whether you recognize it.
• Firewall rules: Most default firewall configurations will block this port, which is fine—it shouldn't need to be open unless you're running something specific that requires it.

How to Use This Port

If you're developing software and need a port number:

• Don't use port 1107 unless you know why: Just because it's obscure doesn't mean it's available for random use.
• Check the IANA registry: Make sure you understand what (if anything) might legitimately use this port.
• Consider the ephemeral range (49152-65535): For temporary or client-side connections, use the dynamic port range instead.
• Register if necessary: If you're building something that needs a permanent port assignment, go through the proper IANA registration process.

Related Ports

• Port 1106: ISOIPSIGPORT-1, the first port in whatever signaling system port 1107 belongs to
• Ports 1024-49151: The full registered ports range, filled with similar obscure and abandoned assignments