Port 309: EntrustTime — The Time Service That Time Forgot

Port 309 is officially assigned to EntrustTime, a time synchronization protocol developed by Entrust Technologies. The port is registered for both TCP and UDP, with Peter Whittaker listed as the contact person in IANA's port registry.¹

This is a well-known port in the official sense—it sits in the 0-1023 range reserved for system services. But it's also something rarer: a registered port that appears to have faded into obsolescence while remaining officially assigned.

What EntrustTime Was

EntrustTime was a time synchronization service from Entrust Technologies, the company that pioneered Public Key Infrastructure (PKI) in the early 1990s. Entrust emerged from Nortel's Secure Networks group and released the world's first commercially available PKI software in January 1994. In December 1996, Nortel spun off Entrust as a separate company.²

The exact technical specifications of the EntrustTime protocol are not well-documented in public sources. What's clear is that it served as a time synchronization mechanism, likely integrated with Entrust's broader security infrastructure during the mid-to-late 1990s.

Why You'll Never See It

Here's the honest truth: port 309 is a ghost port. It's officially registered and appears in every port database, but you're unlikely to ever encounter actual EntrustTime traffic in the wild.

Time synchronization on the Internet is dominated by the Network Time Protocol (NTP), which runs on UDP port 123 and has been the standard since the 1980s. NTP version 0 was implemented in 1985, and by the time Entrust was developing their PKI solutions in the 1990s, NTP was already well-established.³

Entrust's modern timestamping services—which cryptographically timestamp digital signatures to prove when documents or code were signed—use completely different protocols. Today's Entrust Timestamping Authority implements RFC 3161 (the PKIX Time-Stamp Protocol) over HTTP/HTTPS, not the old EntrustTime protocol on port 309.⁴

The Gap Between Assignment and Use

Port 309 represents a particular category of port: officially assigned but practically extinct. IANA doesn't typically revoke port assignments, so EntrustTime remains in the registry even though the protocol itself appears to have been replaced by modern standards.

This is not unusual. The port registry is full of assignments from the 1990s and early 2000s that represented genuine services at the time but have since been superseded by better protocols or abandoned as companies changed direction.

The difference between "assigned" and "actively used" is significant. Port 309 is assigned—there's no question about that. But assignment doesn't mean deployment, and deployment doesn't mean widespread use.

Checking for Activity

If you want to verify whether anything is actually listening on port 309 on your system:

# On Linux or macOS
sudo lsof -i :309
sudo netstat -tuln | grep :309

# On Windows
netstat -an | findstr :309

The odds are high you'll find nothing. And that's fine. Not every assigned port needs to carry traffic. Some ports are historical markers—evidence that someone, somewhere, once built something that needed its own door into the network.

What This Port Teaches Us

Port 309 is a reminder that the Internet's infrastructure contains layers of history. Protocols are designed, deployed, used, and eventually replaced. The port numbers remain as artifacts.

EntrustTime served whatever purpose it needed to serve in the 1990s when Entrust was building the first commercial PKI systems. Those systems evolved. The protocols changed. But the port assignment endures in the registry, a small monument to a protocol that solved a problem we no longer solve that way.

This is normal. This is how infrastructure ages. Some protocols become foundational (like NTP). Others serve their purpose and fade. The port numbers tell both stories.

Related Ports

• Port 123: Network Time Protocol (NTP)—the standard for time synchronization
• Port 37: TIME Protocol (RFC 868)—another legacy time service
• Port 709: Entrust Key Management Service Handler
• Port 710: Entrust Administration Service Handler