Video: X4Online Alpha Footage
What is X4Online?
X4Online is a native C++ extension that turns X4 into a multiplayer game. Not "send a venture and wait" multiplayer — actual real-time multiplayer where you share a universe with other players.
How it works:
- One player hosts. Their game IS the server — the full X4 simulation (NPCs, economy, everything) runs on their end.
- Other players connect as clients. They see the host's universe and interact with it.
- All game state flows through the host. One universe, one truth.
Current Status: Alpha
This is very early. I want to be upfront about that. Right now this is in early alpha, a lot is already working, still a huge amount of work needs to be done to be able to call it "beta".
What works today
- Host/Client connection - Networking between multiple game instances
- "On-Foot" Characters in stations/ships work (Animations need sync still, no running/walking animations for now, Doors need sync too)
- Ships replication (Location, Sector Enter/Leave, Docking - tho ship-crews not yet done)
- Station Replication (certain details not replicated yet)
- Cluster/Sector replication
- Factions replicated (Relations, Ownership of Ships, Stations, Clusters all work)
- SETA blocking - SETA is automatically disabled when players are connected (can't/shouldn't have time acceleration in multiplayer)
- A lot more is already done, like Player-Faction credits etc.
This is an ALPHA, so a lot is missing:
- Economy, trading, cargo, crews
- Combat, weapons, damage
- Fleet management
- A lot of stats, UI, etc.
- ...
Technical Details (for the curious)
- Native C++ extension built on the X4Native framework (another mod by me) — runs inside the game process, no external tools
- Host-authoritative architecture — the host's game is the single source of truth
- FlatBuffers serialization — efficient binary protocol for state replication
- Lock-free threading — network I/O on a background thread, game API calls on the UI thread, bridged with lock-free queues
- ~20Hz state broadcast with client-side interpolation for smooth visuals
- < 1ms per frame overhead on the UI thread
What's Next
The immediate next steps after the current ALPHA:
- Player actions — client commands (fly, dock, trade) sent to host for execution
- Economy & stations — shared economy state
- Combat — weapons, damage, shields
Feedback, questions, and ideas are welcome. Just keep in mind this is early days — "when will X be ready" is hard to answer right now. The focus is on getting the fundamentals rock solid before building up.
Interested in Contributing?
If you're a modder, a C++ developer, or someone who's been itching to get into game modding — I'd love to have help down the line. This is a big undertaking and there's plenty of room for contributors once the foundation stabilizes. More details on how to get involved will follow soon. In the meantime, feel free to reach out if this is something you'd want to be part of.
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