FeverLink3
Play Transport Fever 3 together. Several players build in one shared world, each in their own game.
Playing guide · Changelog · Roadmap · FAQ · Privacy · Architecture
Real time: the road stands on both games 1.4 s after the click at game speed x1 (normal) and 0.8 s at x4 (two games on one PC, a grown save with 6,393 inhabitants). The wait is a safety margin: every game builds at the same game step. In the beta, stability comes first.
What you get
- Built into the game, no separate launcher. Start Transport Fever 3 from Steam as usual: hosting, joining, chat, syncing and updates all live in the game's bottom bar and window. There is no extra program to run.
- Build together. Roads, bridges, tunnels, rail, signals, stations, stops, depots, lines and vehicles: what one player builds appears in every game.
- Your other mods work together too. Mods that change your world by themselves, such as Auto Line Namer, Auto Color Lines or Auto Assign Terminals, stay in sync: the host's copy makes the change and every game applies it at the same moment, and what you set in such a mod's own window reaches every game (new in 0.2.4; seen with two games on one PC).
- The full game. Towns grow, traffic flows, ratings change, exactly as in single player. Nothing is switched off.
- Easy to join. Over Steam: no ports, no router settings, no IP addresses. The host sends a join code, the friend pastes it.
- Steam invites. Invite friends from Steam's own invite dialog; with a world loaded they join by themselves (played between two PCs over the internet).
- Always the same world. The games check each other all the time. If they ever drift apart, everyone gets the host's world back in a few seconds and play goes on.
- Shared speed, pause and chat.
- Encrypted. Everything between the games is encrypted; the join code works like a password.
- One-click bug reports. "Report a problem" collects the logs of every player in the session into one zip, with personal data removed, ready to attach to a GitHub issue.
The interface
A coloured icon in the game's bottom bar shows the session at a glance: white (no session), yellow (waiting), green (in sync), red (needs attention). Click it for the details.
Tested
- Played with friends over the internet, and in long two-game sessions on one PC.
- In a 3.5-hour session over Steam with a friend, an automatic repair was needed about once every 40 minutes (about 15 s each); other mods that change the world on their own can add more.
- About 1,600 automatic tests run on every change: the network protocol, the sessions, the world checks and two complete games simulated side by side.
- A test lab drives two real games with scripts to measure speed and catch drift.
Measured with two games on one PC (internet numbers follow):
| Result |
|---|
| Click to build on both games | 1.4 s at game speed x1, 0.8 s at x4 (the recording above: real time, a grown save with 6,393 inhabitants) |
| World check | every 5 s, without stutter |
| A game freezing for a few seconds | the others play on; it catches up by itself |
| Repair when the worlds differ | about 15 s for a 45 MB world |
Coming next
- Coming back after a short drop without a reload
- Separate companies for each player
FeverLink3 is in beta: keep backups of the saves you play with.
Install
- Download
FeverLink3-<version>.zip from GitHub Releases or Nexus Mods and extract it.
- In Steam, right-click Transport Fever 3 → Manage → Browse local files.
- Drag
winhttp.dll and the mods folder into that folder (merge the folders when Windows asks).
- Start the game, and turn on FeverLink3 Multiplayer in the mod list when you start or load a game.
Host: click the FeverLink3 icon in the bottom bar → Host a game → Copy code and send it to your friend → Start the session when they appear.
Join: open the FeverLink3 window, paste the code (Ctrl+V) and press Join. Only join people you trust.
Everyone needs the same game version. More in the playing guide.
Uninstall: delete winhttp.dll and mods\release\feverlink3 from the game's folder.
Build from source
Needs stable Rust, and Python with lupa for the Lua tests.
cargo test --workspace --exclude feverlink3_native
cargo test -p feverlink3_native -- --test-threads=1
cargo build --release -p feverlink3_native # target/release/feverlink3_native.dll -> ship as winhttp.dll
pip install lupa && python -I -m unittest discover -s tests/lua -p "test_*.py"
powershell -NoProfile -ExecutionPolicy Bypass -File tools\check.ps1 # all of CI's checks at once, a table, exit code 0 = all passed
Issues and pull requests are welcome. Bug reports: GitHub issues (use Report a problem in the game to make the zip); Discord: azalshehri.
License
PolyForm Noncommercial 1.0.0: free to use, study, change and share for noncommercial purposes. For commercial use, ask on Discord.
Credits
FeverLink3 builds on what earlier Transport Fever multiplayer projects found and documented; see THIRD_PARTY_NOTICES.md. It uses the game's official scripting API as described in the Transport Fever 3 modding wiki and the TF3 docs.
Unofficial
FeverLink3 is an unofficial fan project for Transport Fever 3 (Windows, Steam). It is not affiliated with or endorsed by Urban Games or Paradox Interactive. Transport Fever is a trademark of its owners.
