What Port 2759 Is
Port 2759 sits in the registered ports range (1024–49151). These ports are managed by IANA, which accepts formal applications from organizations that want to claim a port for a specific service. Unlike the well-known ports (0–1023), registered ports don't require elevated privileges to open — any process can bind to them.
IANA's registry lists port 2759 as assigned to apollo-GMS on both TCP and UDP.1
Apollo Computer and the GMS Registration
Apollo Computer was a workstation manufacturer founded in 1980 in Chelmsford, Massachusetts. In the early 1980s, Apollo workstations ran a proprietary operating system called Domain/OS, with its own networking stack — the Apollo Domain protocol — predating widespread TCP/IP adoption. At their peak, Apollo workstations were serious competition for Sun Microsystems.
Hewlett-Packard acquired Apollo in 1989 for $476 million.2
The "GMS" in apollo-GMS likely stood for a groupware or group management system — part of Apollo's Domain software suite for coordinating work across networked workstations. The IANA registration for port 2759 is a fossil from that era. The company is gone. The port number carries its name indefinitely, because IANA port assignments don't expire.
Is Anything Using This Port Today?
Not for its registered purpose. Apollo Computer's software hasn't been in active development for over 35 years.
No widely documented malware, peer-to-peer software, or unofficial services have claimed this port as a de facto standard. If you see something listening on port 2759, it's almost certainly application-specific — a developer who chose an available port number, a game server, a local service that picked it arbitrarily.
How to Check What's Listening
On Linux or macOS:
On Windows:
If something appears, the process ID in the last column will tell you what it is. Cross-reference with your process list (tasklist on Windows, ps aux on Linux/macOS) or your application logs.
Why Ghost Registrations Matter
Port 2759 is one of thousands of registered ports tied to products, companies, or protocols that no longer exist. These registrations accumulate in IANA's registry indefinitely.
This matters for two reasons. First, the ports are technically "taken" — a new service wanting that number would need to register a different one. Second, and more practically, seeing a registered port name in a port scanner or firewall log can be misleading. "apollo-GMS" sounds official. It was, once. It isn't now.
When investigating unexpected traffic on registered ports, always check what's actually running — not just what the port's name suggests.
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