Port 697 is officially assigned by IANA to UUIDGEN, a network service created by Sun Microsystems for generating Universally Unique Identifiers (UUIDs) over the network.1 It operates on both TCP and UDP protocols.
You probably have the uuidgen command-line tool on your system right now. But the network service on port 697? That's from an era when UUID generation was something you requested from a server, not something you did locally.
What UUIDGEN Was
UUIDGEN was a network service that generated 128-bit UUIDs—unique identifiers in the format like 550e8400-e29b-41d4-a716-446655440000. The service was registered with IANA by James Falkner from Sun Microsystems (jhf@eng.sun.com).2
When a client connected to port 697, the server would generate and return a UUID. This guaranteed uniqueness across distributed systems without requiring clients to implement the UUID generation algorithm themselves or worry about collisions.
Why It Existed
In the 1990s, distributed systems faced a real problem: how do you generate identifiers that are guaranteed to be unique across multiple machines without coordination?
The options were:
- Central counter — But what if the server goes down?
- Local generation — But what if two machines generate the same ID?
- UUID service — Ask a dedicated server to generate unique IDs
UUIDGEN was the third approach. It centralized UUID generation so systems could trust the uniqueness without implementing the algorithm themselves.
What Happened to It
The service became obsolete because the problem disappeared. RFC 4122 (published in 2005) standardized UUID generation algorithms that could be implemented locally.3 The algorithms use:
- Time-based UUIDs (v1) — Current timestamp + MAC address + random bits
- Random UUIDs (v4) — Cryptographically strong random numbers
- Name-based UUIDs (v3/v5) — Hash of a namespace and name
With these algorithms, every system can generate its own UUIDs with collision probability so low it's effectively zero. The 128-bit space is so vast that even generating a billion UUIDs per second for 100 years would have less than a 50% chance of a single collision.
The network service wasn't needed anymore. Generation moved from servers to libraries. Every modern programming language has a UUID library built in.
The Philosophy Shift
Port 697 represents a fascinating shift in computing philosophy.
The UUIDGEN service said: "Trust the server. It will give you unique IDs."
Modern UUID generation says: "Trust the algorithm. The probability space is so large that collisions are mathematically implausible."
This is the same shift that happened across distributed systems—from central authorities to local autonomy. From asking permission to acting independently with confidence that the math works out.
Today
Port 697 is still officially assigned to UUIDGEN in the IANA registry, but the service itself has effectively vanished. You won't find it running on modern systems.
What you will find is the uuidgen command-line utility on nearly every Unix-like system:4
Same name. Different implementation. No network required.
The port remains as a historical marker—a reminder of when unique identifiers were something you requested from a server rather than something you generated in a single function call.
Related Ports
- Port 111 — Portmapper/rpcbind, the RPC service that UUIDGEN likely registered with
- Port 407 — Timbuktu, another Sun Microsystems network service from the same era
Checking Port 697
To see if anything is listening on port 697:
Linux/macOS:
Windows:
You almost certainly won't find anything. The service belongs to computing history.
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