Port 594 is officially assigned to TPIP for both TCP and UDP.1 The protocol name likely stands for Transaction Processing over IP, though even this is uncertain. TPIP was registered with IANA at some point in Internet history, claimed its spot in the well-known port range, and then quietly faded into obscurity.
Finding a running TPIP service on port 594 in 2026 would be remarkable. The protocol exists in official registries but has essentially vanished from practice.
What Is TPIP?
The honest answer: we don't entirely know anymore.
The most likely explanation is that TPIP refers to some form of transaction processing protocol designed to run over TCP/IP networks. In the 1990s and early 2000s, various protocols were developed for distributed transaction management—coordinating database operations across multiple systems to ensure consistency.
Some sources suggest TPIP might be related to the Transaction Internet Protocol (TIP), defined in RFC 2371, which provides two-phase commit functionality for distributed transactions.2 However, TIP typically doesn't use port 594, and the relationship between TPIP and TIP remains unclear.
There's also a modern protocol called tpIP (lowercase)—a time-predictable TCP/IP stack for cyber-physical systems—but this is unrelated to the TPIP assigned to port 594.3
The protocol is a ghost. Officially registered, rarely documented, almost never seen.
Why Port 594 Matters
Port 594 sits in the well-known port range (0-1023), which IANA reserves for important, widely-used services. To get a port in this range, you need IANA approval. The intention was to prevent conflicts and ensure critical protocols had stable, predictable port assignments.
But intention and reality diverge. The well-known port range contains dozens of ports like 594—officially assigned to protocols that either never gained traction or have been abandoned. They're placeholders in a registry that nobody updates when protocols die.
This matters because:
- Port scanners will flag it — Security tools recognize port 594 as TPIP, even though they've probably never encountered actual TPIP traffic
- It can't be reassigned — Port 594 is taken. Even though TPIP is functionally dead, IANA won't give this port to something else
- It shows how the Internet ages — Protocols get registered, services get built, companies disappear, and the port assignments remain
Checking What's On Port 594
If you find port 594 open on a system, it's almost certainly not TPIP. To check what's actually listening:
Linux/Mac:
Linux (alternative):
Windows:
If something is running on port 594, it's likely:
- A misconfigured service that chose a random port
- Malware using an obscure port to avoid detection
- A custom application that didn't check what port 594 was supposed to be for
The Well-Known Port Graveyard
Port 594 isn't alone. The well-known port range (0-1023) is full of these assignments:
- Protocols that were designed but never widely implemented
- Services that were critical in the 1980s but irrelevant now
- Corporate protocols that died when the company folded
- Academic experiments that never left the lab
The IANA registry is a museum. Some exhibits are still in use (port 80 for HTTP, port 443 for HTTPS). Others are fossils. Port 594 is a fossil.
Security Considerations
If port 594 is open on your systems:
- Investigate immediately — it shouldn't be
- No legitimate modern service should be using this port
- It's either misconfiguration or something deliberately hiding
Don't trust the label:
- A port scanner might identify traffic on 594 as "TPIP"
- That identification is based on IANA's registry, not actual protocol analysis
- Verify what's actually running before assuming it's harmless
What This Port Teaches Us
Every port tells a story. Port 594's story is about the gap between official assignments and actual use. IANA can designate a port. They can add it to the registry. They can call it "well-known." But they can't make people use it.
The Internet is built on consensus, not authority. Port 594 has authority—it's officially assigned. But it lacks consensus. Nobody agreed to actually use it. And in the end, consensus wins.
The port exists. The protocol doesn't. And somewhere in IANA's registry, port 594 waits for a service that's never coming back.
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