Port 1120 carries the files that built one of gaming's most enduring online communities. Every patch download, every custom map, every content update that flowed through Blizzard's Battle.net service traveled through this port.
What Runs on Port 1120
Port 1120 is officially registered with IANA for bnetfile—the Battle.net File Transfer Protocol.12 It operates on both TCP and UDP, handling file transfers for Blizzard Entertainment's online gaming platform.
The protocol works alongside port 1119 (bnetgame), which handles chat and game coordination. While 1119 manages the social and matchmaking aspects, 1120 quietly moves the actual files—patches, maps, game assets, and updates.
How It Works
When you launch a Blizzard game and it needs to download an update, port 1120 opens the connection for that transfer. The Battle.net desktop app, the Blizzard Downloader, and games like World of Warcraft, StarCraft, Diablo, and Hearthstone all use this port.3
The protocol uses TCP for reliable file delivery—when you're downloading a 2GB patch, you need every byte to arrive intact and in order. Some operations also use UDP for faster, less critical transfers where occasional packet loss is acceptable.
The Battle.net Story
Battle.net launched on December 31, 1996, followed days later by Diablo on January 3, 1997.4 It was revolutionary: the first online gaming service built directly into the games themselves. No external launcher. No separate login screen. You bought Diablo, installed it, clicked "Battle.net," and you were in.
This seamlessness required protocols that just worked. Port 1119 handled chat and game sessions. Port 1120 handled the files. Together, they created an experience that felt magical in 1997—and still works today.
By November 1997, Battle.net had 1.25 million users, with 3,500 new registrations daily and 2.2 million games played.4 When StarCraft launched in 1998, usage exploded. The infrastructure that made it possible included these two ports, quietly doing their jobs while millions of players battled across Aiur and Sanctuary.
The service evolved through multiple generations—Battle.net 2 launched around StarCraft II's release—but the ports remained.5 Port 1120 has been transferring Blizzard game files for nearly three decades.
Security Considerations
Port 1120 is a legitimate service port, but like any network service, it should only be accessible when needed:
- Firewall rules: If you're not running Blizzard games, this port should be blocked
- Game updates only: Modern Battle.net primarily uses HTTPS (port 443) for downloads, with port 1120 used for specific game-related transfers
- Local network: The port typically connects outbound to Blizzard's servers; you shouldn't need to forward it inbound unless troubleshooting specific connection issues
If you see unexpected traffic on port 1120 and you're not running Blizzard software, investigate. While the port is legitimately registered, anything can listen on any port.
Related Ports
Port 1120 works as part of the Battle.net infrastructure:
- Port 1119: bnetgame—handles chat, authentication, and game session coordination5
- Port 3724: World of Warcraft game server connections
- Port 6112: Legacy Battle.net protocol (Diablo, StarCraft, Warcraft II)
- Port 443: HTTPS—modern Battle.net uses encrypted web connections for most operations
Checking What's Listening
To see if something is using port 1120 on your system:
Linux/Mac:
Windows:
You'll typically see this port active only when the Battle.net launcher is running or when a Blizzard game is downloading updates.
Why This Port Matters
Port 1120 represents a moment in Internet history when online gaming was finding its shape. Blizzard didn't just build games—they built the infrastructure that made playing together seamless.
The port is still registered, still in use, still transferring files for games played by millions. It's a reminder that behind every game session, every download, every moment of connection, there are protocols doing exactly what they were designed to do decades ago.
Every time you've downloaded a World of Warcraft patch, every StarCraft map you've played, every Diablo update—port 1120 was there, moving the bytes that made it possible.
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