The Complete Guide to Hosting Black Ops 3 Servers on Boiii: Multiplayer & Zombies
Three common issues account for the vast majority of broken servers: ghost processes, binding failures, and master server communication dropouts. If your server executes and instantly closes within two seconds, check the root directory for a generated crash dump. Missing asset caches or a corrupted server.cfg encoding trigger instant crashes on startup.
If your batch file runs cleanly without errors, but friends cannot see your room listed in the in-game BOIII server browser, test these critical failure points:
First, test external visibility using an open port checking tool against your public external IP on port 27017 UDP while the batch file runs. If the port reports closed or filtered, your router did not apply the rule correctly, your static local IP drifted, or your ISP utilizes CGNAT (Carrier-Grade Network Address Translation). If your internet provider routes your connection through CGNAT, external packets cannot reach your router directly. You will need to request a static public IP from your ISP or establish a private tunneling mesh like Tailscale or ZeroTier across all connecting clients.
Second, resolve local client joining errors. Players on your local home network must connect using your internal LAN address (for example, typing /connect 192.168.1.185:27017 into the in-game console). Attempting to connect via your external public IP from inside the same local network will fail unless your router natively supports NAT Loopback (Hairpinning).
