Port 1175 occupies a strange space in the Internet's port registry. It has official assignments from IANA—dossier server on UDP and indigo-server on TCP—but if you search for information about these services, you'll find almost nothing. No documentation. No active communities. No modern software that uses them.
This is a ghost port. Officially assigned, practically abandoned.
What Range This Port Belongs To
Port 1175 sits in the registered port range (1024-49151). These ports are assigned by the Internet Assigned Numbers Authority (IANA) to specific services upon request. Unlike well-known ports (0-1023) which require special privileges, registered ports can be used by regular user applications.
The registration process means someone, at some point, requested port 1175 for their service. IANA approved it. The assignment went into the official registry. And then... the service faded away.
The Official Assignments
According to the IANA registry, port 1175 has two assignments:1
UDP 1175: dossier Listed as "Dossier Server" with no additional documentation. Searches for this service turn up only port databases that copy the IANA registry. No protocol specification. No software implementation. No user community. Just a name in a list.
TCP 1175: indigo-server Listed as "Indigo Home Server" but likely obsolete or incorrect. The actual Indigo Domotics home automation software uses port 1176 for its server, not 1175.2 Whether port 1175 was used in an earlier version, or whether this is a registration error, is unclear.
Why This Happens
The port registry is not just a list of active services. It's also an archive.
Protocols get developed, assigned a port, and then abandoned when the technology doesn't catch on. Companies register ports for proprietary software that later gets discontinued. Standards get superseded by better alternatives. The registry remains, but the services disappear.
Port 1175 is one of thousands of these registered-but-unused ports. Someone needed it once. Nobody needs it now.
What Might Actually Be Using This Port
In practice, port 1175 is available for use by any application that needs a listening port. You might find:
- Custom internal applications that chose an available registered port
- Malware that picked a random port number for command and control
- Legitimate software that happens to use this port without official assignment
- Nothing at all
How to Check What's Listening
If you want to see if anything is actually using port 1175 on your system:
On Linux/macOS:
On Windows:
If something is listening, you'll see the process ID. You can then identify what application opened that port. More often than not, you'll find nothing.
Why Unassigned Ports Matter
The port number system has 65,535 available ports. The well-known ports (0-1023) are tightly controlled. The registered ports (1024-49151) have loose assignments like port 1175. The dynamic/private ports (49152-65535) are completely unassigned.
This three-tier system provides flexibility. Applications can request official registration for visibility and collision avoidance, or they can use dynamic ports that are assigned temporarily by the operating system.
Ports like 1175—registered but unused—sit in an awkward middle ground. They're not available for dynamic allocation, but nobody's using them for their registered purpose either. They're reserved for ghosts.
The Honest Reality
Port 1175 exists in the registry because someone, years ago, thought they needed it. The dossier server, whatever it was, is gone. The indigo-server reference appears to be a mistake or an abandoned early version.
What remains is a line in a database and a port number that's technically assigned but practically available.
This is normal. The Internet is built on layers of abandoned infrastructure, deprecated protocols, and services that nobody remembers. Port 1175 is one small example—a ghost in the registry, waiting for someone who will never call.
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