The original XLabs project was shut down via a DMCA. Community forks have risen to replace it. If you have an old 2022 build, the master server URL is hardcoded to a dead address. You need a modern fork (search GitHub for "iw4x client 2025").
This paper provides a complete reference for developers, players, and server administrators working with the IW4x server list.
| Packet Type | Direction | Description | |-------------|--------------------|-------------------------------------------| | 0x01 | Client → Master | Request server list (with optional filters) | | 0x02 | Master → Client | List of servers (compressed) | | 0x03 | Server → Master | Heartbeat registration | | 0x04 | Master → Server | Acknowledgment / rejection |
Look for the "Mod" column. If it says "None," it is vanilla. If it says "Bot_Mod" or "MW2Mod," expect chaos.