Port 344: PDAP — The Directory Service That Tried to Organize the Internet

Port 344 is officially assigned to PDAP (Prospero Data Access Protocol) for both TCP and UDP. You've probably never heard of it. Almost no one uses it anymore. But in the early 1990s, it represented a genuine attempt to solve a problem that was keeping people up at night: how do you organize the Internet?

What PDAP Does

The Prospero Data Access Protocol was the communication layer for the Prospero File System, a distributed directory service created by B. Clifford Neuman at USC's Information Sciences Institute.¹ Available since December 1990, Prospero let users construct their own personalized views of Internet resources—files, services, data—by organizing them into custom virtual file systems.²

Think of it as a way to build your own map of the Internet. You could take resources from FTP servers, Andrew File System, Sun NFS, and other sources, then arrange them into a structure that made sense to you. The system provided "object-centered naming"—naming without requiring a global context.³

The Problem It Was Solving

In the early 1990s, the Internet was exploding. Resources were scattered across thousands of servers. There was no Google. No Yahoo directory yet. Finding things was genuinely hard, and once you found them, remembering where they were was harder.

Prospero tried to solve this by giving users tools to organize what they found. You could create directories, share your organizational structures with others, and build on the structures other people had created. It was collaborative information organization before anyone called it that.⁴

The protocol also powered the Archie system's client-server communication—Archie being one of the earliest Internet search tools for finding files on FTP servers.⁵

Why It Disappeared

Prospero was technically sophisticated and conceptually elegant. It just wasn't what the Internet needed.

Search engines happened. Web browsers happened. The web's hypertext model turned out to be a more natural way for people to organize and discover information than building custom file system hierarchies. By the late 1990s, Prospero had faded into obscurity.

The official Prospero website still exists as a historical artifact, but there's no evidence of active development or use in the modern Internet. Port 344 remains assigned to PDAP in the IANA registry, a permanent reservation for a protocol that almost no one runs anymore.

The Person Behind It

B. Clifford Neuman, who created Prospero, went on to more influential work. After graduating from MIT in 1985, he spent a year at MIT's Project Athena where he became a principal designer of Kerberos, the authentication system that actually did change the world.⁶ Version 5 of Kerberos, which Neuman co-designed with John Kohl, is still widely used today for network authentication.⁷

Prospero didn't survive, but Neuman's contributions to Internet security through Kerberos are fundamental to how authentication works on modern networks. Not every protocol wins, but the people who design them often go on to build the ones that do.

Security Note

Some security databases have flagged UDP port 344 as being associated with malware or trojans in the past.⁸ This doesn't mean the Prospero protocol itself was malicious—it means attackers sometimes reused the port number for their own purposes, knowing it was rarely monitored. This is common with assigned-but-unused ports.

Why This Port Still Matters

Port 344 is a well-known port (0-1023), which means it's part of the IANA-managed registry reserved for system services. Even though Prospero is obsolete, the port remains officially assigned. This is how the Internet preserves its history—port numbers aren't recycled lightly.

If you see traffic on port 344 today, it's worth investigating. It's almost certainly not legitimate Prospero traffic. On modern systems, check what's listening:

# Linux/Mac
sudo lsof -i :344
sudo netstat -tulpn | grep :344

# Windows
netstat -ano | findstr :344

The Lesson

Port 344 reminds us that the Internet's evolution isn't inevitable. Smart people built Prospero to solve a real problem, and it worked technically. But the web solved the same problem in a way that felt more natural to users, and Prospero became a historical footnote.

The port remains assigned. The RFC documentation remains archived. And somewhere in the IANA registry, port 344 still carries the name of a system that tried to bring order to the Internet's chaos, even if the Internet found a different path.

Related Ports

• Port 191 — Prospero Directory Service (another port assigned to the Prospero system)
• Port 21 — FTP, one of the systems Prospero interfaced with
• Port 88 — Kerberos, the authentication system Neuman went on to help design