Port 3724: Unassigned — The World of Warcraft Port

Port 3724 sits in the registered port range (1024–49151) but carries no official IANA assignment. On paper, it belongs to no one. In practice, it belongs to Azeroth.

The Registered Port Range

Ports 1024 through 49151 are registered ports. The idea is that software vendors apply to IANA, receive an assignment, and the port gets formally documented. The system keeps ports from colliding — two applications accidentally picking the same number and stepping on each other.

But registration is voluntary. Applications can use any port they like. Port 3724 is a case where a massive, globally deployed application never went through the formal process. It just picked a number and used it, and enough people used the software that the port became famous anyway.

What Actually Runs on Port 3724

World of Warcraft — Blizzard Entertainment has used port 3724 since WoW launched in November 2004. It's the primary connection port: TCP 3724 carries the game client's connection to Blizzard's servers, handling authentication and gameplay traffic. UDP 3724 was used for in-game voice chat.

At WoW's peak, roughly 12 million subscribers worldwide were connecting through this port. Router forums filled with "how do I open port 3724" threads. Network admins at universities and offices added it to blocklists. Parents added it to parental controls. For better or worse, 3724 became one of the most socially significant port numbers of the 2000s.

Club Penguin — Disney's children's multiplayer game also used port 3724 for client-server connections before the game was shut down in 2017. Two games, one port, no official registration.

Security Considerations

Unassigned ports used by popular software are attractive targets. Blizzard's authentication servers have been subjected to DDoS attacks over the years, with 3724 as a natural chokepoint. If you're not playing WoW, there's no reason this port should be open inbound on your network.

Private WoW server software (emulators of Blizzard's servers) also listens on 3724 by convention — honoring the original port assignment even in unofficial implementations.

What's Listening on Your Machine

To check what process, if anything, is using port 3724:

# macOS / Linux
sudo lsof -i :3724

# Windows
netstat -ano | findstr :3724

If you're not running WoW or a game server, nothing should answer.