TI Multiplayer

TI Multiplayer (in the game: Terra Invicta Multiplayer, on Steam: Terra Invicta Multiplayer [EA]) is a mod that adds real multiplayer to Terra Invicta. Play the full campaign together with friends, each with your own faction or two of you sharing one, or fight a quick 1v1 space battle.

The mod is in Early Access. Retrofitting multiplayer into a game that was not built for it is a big undertaking: expect bugs and occasional desyncs, especially in long campaigns, and keep backups of your saves. Multiplayer saves and single-player saves cannot be converted into each other.

New in 0.8.0

• Co-op - two players can share one faction.
• Combat autosave - the host saves before every battle with players, see Saves and Sessions.
• Players who come back into a continued session get their faction and co-op role back automatically.
• A warning 30 seconds before an unanswered decision is skipped.
• Many changes now reach the other players at once, and many fixes for battles, habs, the council phase and host migration. The full list is in the change notes on the Workshop page.

Game modes

Mode	Players	What you play
Sandbox campaign	2 - 8 per lobby	The normal campaign. Each player claims one of the seven human factions. The AI plays every unclaimed faction and the aliens. With co-op two players can share one faction.
Skirmish	exactly 2	A single 1v1 tactical space battle, set up and started from the main menu. No campaign, no save.

How it works

• The host runs the game. Only the host's computer simulates the world. The other players (clients) see the same world in real time, and every order they give is sent to the host and carried out there. If host and client disagree, the host is right.
• Real time, not turns. Everyone plays at the same time on the same clock. The host controls the game speed, and anyone can pause. When the game waits for a decision of another player, the clock stops for everyone - see Time and Decisions.
• Exact match required. All players need the same Terra Invicta build (1.0.53a and 1.0.53b count as different), the same TI Multiplayer version, the same multiplayer-aware mods in the same versions, and any DLC the chosen scenario requires. Differences are refused when joining, with a message that names the difference.
• Steam networking. By default the connection runs over the Steam relay network - no port forwarding needed. A direct connection over UDP (port 7777) is also possible.

Installation

1. Install Unity Mod Manager into Terra Invicta (see Installing mods). On Linux, use GE-Proton or a Proton version 10 or newer.
2. Subscribe to Terra Invicta Multiplayer on the Steam Workshop.
3. Start Terra Invicta through Steam and enable the mod in the in-game Mods menu.
4. Press Ctrl + F10 and set your Player Name in the mod settings before your first session, so the others can recognize you.

Getting started

Hosting a campaign

1. In the main menu click MULTIPLAYER, then Create new session.
2. In the lobby room, use Toggle Mode until the mode shows Sandbox Campaign.
3. Optionally set a title, a password and co-op in Lobby Settings, and the scenario and options in Campaign Settings.
4. Claim your faction. Wait for your friends to join and claim theirs.
5. Click Start Game. You need at least two human players.

Joining

1. Click MULTIPLAYER, select the session in the Steam Lobbies list (or accept a Steam invite) and click Join.
2. Claim a free faction and wait for the host to start.

Details, including joining a game that is already running, are on Hosting and Joining.

Features

• Hosting and Joining - Lobby browser, Steam relay and Direct Connect, the lobby room, passwords, campaign settings and faction names, joining a running game (hot-join), leaving and rejoining, and what happens when the host leaves (host migration).
• Time and Decisions - Who controls the clock, why it stops, what happens when a player does not answer an event, and how the councilor mission phase works with several players.
• Saves and Sessions - The shared session save, monthly autosaves, manual and combat saves, and continuing a campaign.
• Co-op - Two players controlling one faction: who decides what, joint council confirmation and fighting battles together.
• Combat - Tactical space battles in the campaign: player versus AI (another player may fly the AI side), player versus player, spectators and the battle clock.
• Skirmish - The 1v1 battle mode.
• Diplomacy and Chat - Trading between players (including ships and control points), chat, notifications and Steam Rich Presence.
• Settings and Troubleshooting - All mod settings, log files, common messages and how to fix them.
• Mod Compatibility - Which other mods work in multiplayer, and how mod authors connect their mod.

Compatibility

• Multiplayer-aware mods: TI Fleet Manager, TI Space Nations and TI Missile Rework. They are checked automatically when a player joins.
• Mods that only change game data are not checked - every player must install exactly the same ones.
• Other code mods are not supported in multiplayer and can cause desyncs. See Mod Compatibility.
• DLC: a host who owns a DLC can host the base game for players without it. Only scenarios that require a DLC (for example the Dark Skies scenarios) need it on every machine.

Known issues

• Offline players' factions are not really played by the AI. The lobby says Offline - AI takes over, but on the strategy map the faction mostly waits for its player: its open decisions are skipped after 5 minutes, its tactical battles are auto-resolved, and the council phase may need the host to close it. The faction is kept for its player to rejoin.
• The mod setting Use Steam Lobbies currently has no effect.
• Global narrative events (events that concern everyone) are decided by the host's faction only. The other players see them without option buttons.
• If a player disconnects in the middle of a trade negotiation, the clock may stay paused. The host can save and reload the session.
• After a host migration the campaign can roll back to the new host's last copy of the session, the lobby password is removed, and a running battle is called off without result.
• When the host leaves the lobby before the game has started, the other players see a "host migration failed" message instead of "lobby closed".
• Late-game saves are 50 MB and more. Expect short pauses when the full game state is sent (joining, reconnecting).

To report a bug, post in the MOD BUG Multiplayer EA thread on the Pavonis Interactive Discord and attach the Player.log of everyone involved (see Log files).

Credits

Testing and translations by the community. The full list of testers and translators is on the Workshop page.

See also

• Mods - other community mods
• Game Options - the campaign options the host sets in Campaign Settings