Port 1717: fj-hdnet — Claimed but Uncrowded

Port 1717 sits in the registered port range (1024–49151). These ports are formally tracked by IANA—the Internet Assigned Numbers Authority—meaning any vendor can apply to register a port for their service. Registration doesn't mean widespread use. It means someone filed the paperwork.

For port 1717, that someone was Fujitsu, who registered the name fj-hdnet for both TCP and UDP. What fj-hdnet actually does is unclear from public documentation—it appears to be an internal Fujitsu networking service that never achieved broader adoption. The port is technically claimed. In practice, it's nearly vacant.

What's Actually Been Seen on This Port

Because the legitimate occupant is so obscure, port 1717 has attracted squatters:

• America's Army — The US Army's free-to-play recruitment game used port 1717 UDP for game traffic in some versions. A memorable case of military software and military marketing sharing the same port.
• Microsoft Convoy (WLBS) — Windows NT/2000's Windows Load Balancing Service used this port for cluster communication. Convoy was Microsoft's early attempt at network load balancing before it was replaced by NLB in later Windows versions.
• Various enterprise middleware — Port databases list references to IBM WebSphere and Pervasive PSQL connections here, though these appear to be edge cases rather than standard configurations.

None of these are official assignments. They're what happens when a port is technically claimed but effectively empty.

How to Check What's Listening

If you see traffic on port 1717 and want to know what it is:

On Linux or macOS:

# Show what process is listening on port 1717
sudo ss -tlnp | grep 1717
# or
sudo lsof -i :1717

On Windows:

netstat -ano | findstr :1717

The process ID in the output will tell you which application owns the port. On Windows, you can cross-reference the PID in Task Manager.

Why Registered Ports Can Be Ambiguous

The registered port range exists to reduce collisions—if your software claims port 1717 with IANA, other vendors are supposed to pick something else. But registration is voluntary, enforcement is nonexistent, and fj-hdnet was obscure enough that other software simply moved in anyway.

This is common across the registered range. A port can be "assigned" on paper while being effectively available to whoever arrives first. The IANA registry is a coordination mechanism, not a lock.

If you're building software and need a port in this range, checking the IANA registry is the right first step—but also worth checking what's actually in use on your network and in your users' environments.

• Port 1717 (tcp/udp) :: SpeedGuide
• Service Name and Transport Protocol Port Number Registry — IANA
• Port 1717 TCP UDP | fj-hdnet