The Tool Desk
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This guide covers both approaches, including Workshop mod-pack deployment, the official server-management script, Docker, configuration, networking, updates, backups, and the fixes for the most common connection and mod-mismatch errors.
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Choose the right way to host
Your choice depends mainly on whether the world must run without a player hosting it. Calamity is a tModLoader mod, so every option below uses the tModLoader client and server stack.
Host & Play: best for occasional sessions
Host & Play is the shortest path for a small group. One player launches tModLoader, enables the shared mods, selects Multiplayer → Host & Play, chooses a world, and invites the others. The host computer runs the world and must remain in the session. This avoids server administration and is usually the best choice for a group that plays at scheduled times.
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Dedicated tModLoader server: best for a persistent world
A dedicated server runs separately from the players’ game clients. You can leave it online, restart it after a crash, schedule maintenance, and let people join while the usual host is away. You administer the world file, configuration, mod directory, backups, and network exposure yourself.
Docker deployment: repeatable isolation
Docker packages the server and its dependencies in a repeatable environment. It is useful when you want an isolated deployment, predictable upgrades, or easy migration between machines. The official tModLoader utilities document supplied compose files and detached operation.
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A managed game host can handle the operating system, service startup, and network address. Before paying, confirm that the current service supports tModLoader rather than only vanilla Terraria, allows access to the Mods and world directories, provides backups, supports the required geographic region, and permits the mod versions your group uses. Prices, limits, and compatibility change, so verify them directly with the provider.
| Option | Uptime | Administration | File control | Network work | Best fit |
|---|---|---|---|---|---|
| Host & Play | Only while the host is playing | Low | Full control on the host computer | Often simple for invited friends; remote access can still require network setup | Small, occasional group |
| Self-managed dedicated server | As long as the machine and service run | High | Full control of Mods, worlds, and configuration | Firewall and router forwarding normally required | Persistent world and maximum control |
| Docker | As long as the container host runs | Medium to high | Controlled through mounted data directories and compose settings | Firewall and router or provider rules still apply | Repeatable, isolated deployments |
| Managed host | Depends on the provider and plan | Lower day-to-day administration | Varies; verify mod and world-folder access | Usually handled by the provider | Players who do not want to administer a machine |
Requirements before you start
- A legal Terraria installation and tModLoader installed through Steam. tModLoader is distributed as a separate Steam game and has Windows, macOS, and Linux client support.
- The Calamity Mod installed through the tModLoader Workshop. Calamity must be installed with tModLoader; a vanilla Terraria server executable cannot load it.
- The same enabled mod set and compatible versions on every player’s client and on the server.
- For a dedicated server, a computer or hosted instance that can run tModLoader, persistent storage for world and mod files, and permission to open the chosen network port.
- For a home server, access to the host firewall and router. Remote players need the selected port forwarded to the server machine.
No authoritative source establishes a Calamity-specific RAM, bandwidth, or hosting-price requirement. Avoid choosing a machine from an invented minimum; start with a supported operating system, reliable storage, and enough capacity for your own player count and mod set.
Install Terraria, tModLoader, and Calamity
- Install Terraria from Steam on the computers that will play.
- Install tModLoader from Steam. Launch tModLoader rather than the vanilla Terraria entry when you want Calamity.
- In tModLoader, open the Workshop browser and subscribe to the official Calamity Mod and the other mods your group has agreed to use.
- Restart tModLoader if the Workshop installation requests it, then open the Mods menu and confirm that Calamity is enabled.
- Have every player install the same mods before attempting to join. A player who launches vanilla Terraria, or who has a different mod version, will not be able to participate in the Calamity session.
Do not use unofficial Calamity builds or redistribute the mod files. The project warns that unauthorized builds can prevent multiplayer mod synchronization. Let the Workshop installation provide the files on each client and on the server.
Create one authoritative mod pack
A shared pack prevents small differences in enabled mods from turning into join failures. Make the pack on one tModLoader client and treat it as the source of truth for the server and all players.
- Enable Calamity and every companion, library, and quality-of-life mod that the group will use.
- Open Workshop → Mod Packs.
- Select Save Enabled as New Mod Pack, give the pack a clear name, and then choose Open Mod Pack Folder.
- Copy both
install.txtandenabled.jsoninto the dedicated server’sModsdirectory. Keep both files together. - Distribute the pack’s mod list to players, or have them create the same pack through their own Workshop subscriptions. Confirm that the enabled order and versions match before connecting.
Workshop identifies mods by IDs rather than display names. That is why install.txt and enabled.json are more reliable for repeatable deployment than a hand-written list of names. When you change the pack, export the updated files and apply the same change to every client and the server as one coordinated update.
Fast setup with Host & Play
Use this method when the host will be present for the entire session.
- Launch tModLoader and open the Mods menu.
- Enable the agreed Calamity pack and verify that no unexpected mods are active.
- Choose Multiplayer → Host & Play.
- Create a new world or select an existing world. Let the host finish loading it before inviting anyone.
- Invite friends through Steam where available, or provide the connection details shown by the game.
- Have each player join with the identical enabled mod list and compatible versions.
Host & Play is not a 24/7 server. Closing the host’s game ends the session, and the world is unavailable until that player launches and hosts again. Make a world backup before major mod changes even when you use this simpler method.
Deploy a dedicated tModLoader server
Use the official management script
The documented manage-tModLoaderServer.sh tooling can install tModLoader through SteamCMD or GitHub, install Workshop mods, and start the server. Use it when you want direct control of the server filesystem and a conventional service process.
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- Prepare a supported machine and a persistent directory for the server.
- Install the management script and use its documented install operation to obtain the intended tModLoader release.
- Place the exported
install.txtandenabled.jsonin the server’sModsdirectory, or use the script’s Workshop installation commands. - Place an existing
.wldworld in the configured worlds directory, or configure automatic world creation. - Create a server configuration file and set the world, player limit, port, password, mod path, and optional mod pack.
- Start the service with
./manage-tModLoaderServer.sh startand watch the console for mod-loading or world-loading errors.
Use Docker
Docker is appropriate when you want the deployment described as configuration rather than as a manually modified machine. Use the supplied tModLoader compose files, mount persistent locations for worlds, Mods, and configuration, and run the service detached. Keep those mounted directories outside the disposable container layer so a recreation does not erase the world.
- Install Docker and confirm that the host can run the supplied compose configuration.
- Copy the official compose files into a dedicated project directory.
- Mount persistent directories for the world files,
Mods, logs, and server configuration. - Place the authoritative
install.txtandenabled.jsonin the mounted Mods location. - Set the published port to the same port configured inside the server, using 7777 unless you have a reason to change it.
- Start the stack in detached mode and inspect the container logs until the world is ready.
Docker does not remove the need for compatible client mods or network rules. It only changes how the server process and its files are packaged.
Configure the server
Create or copy serverconfig.txt and set the values that define the world and how clients reach it. The documented player-cap range is 1–255, with a default of 8.
| Setting | Purpose | Example or documented value |
|---|---|---|
world= |
Selects the .wld file to load. |
Path to the world file you want this service to run. |
| Automatic world creation | Creates a new world when you do not have a world file. | Use the server’s documented autocreate options instead of supplying an existing .wld. |
maxplayers= |
Sets the player cap. | 1–255; default 8. |
| Sets the listening network port. | 7777 by default. |
|
password= |
Requires a password before joining. | Choose a non-obvious value for a private server. |
modpath= |
Points the server at its Mods directory. | Use the directory containing the installed Workshop files and pack manifests. |
modpack= |
Loads a specific enabled mod pack for the world. | Reference the intended enabled.json pack. |
Launch the server with the configuration file so unattended restarts use the same settings every time. Keep the configuration under backup alongside the world and mod-pack manifests. If you change Calamity settings through a server configuration file, fully quit and restart Terraria before expecting those settings to take effect.
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Make the server reachable
On the host machine
Allow the selected port through the operating-system firewall. If the server listens on the default, that is TCP port 7777. Confirm that the server process is actually listening on the same port before troubleshooting the router.
On a home network
Remote players need a router rule that forwards the selected external port to the internal address of the server machine. Give that machine a stable local address so the forwarding rule does not point to a different device after a DHCP lease changes. Players on the same LAN may be able to connect using the local address even when the public route is not working.
For hosted or tunneled deployments
A provider may supply a public address and handle port exposure. A tunnel or VPN can avoid opening a home router, but it adds another service to administer. In every case, give players the correct public address and port, and do not publish a private password in a public channel.
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Test the server with a second client before inviting the whole group. The following checks catch most deployment mistakes:
- The console identifies tModLoader and loads Calamity rather than starting a vanilla server.
- The server reads
install.txtandenabled.jsonfrom the intended Mods directory. - The selected world loads and saves without errors.
- A second client using the same pack can join, move, open chests, and reconnect.
- Calamity content, including its expected items and bosses, is present.
- The configured password and player cap behave as expected.
- A clean shutdown followed by a restart preserves the world and configuration.
- A remote test from outside the LAN succeeds if the server is intended for internet players.
These are operational checks you should perform on your own deployment; they are not a claim that a particular server has been tested here.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Updates and version control
Modded worlds are sensitive to version drift. Update the server and all clients as a coordinated change, not one computer at a time while players are still joining.
- Back up the world, configuration,
install.txt, andenabled.json. - Record the currently working tModLoader and mod versions.
- Update the server using the management script’s documented install or update command, or rebuild the Docker image according to its deployment instructions.
- Update the clients to the same tModLoader release and Workshop mod versions.
- Start the server and test world loading with one client before reopening it to everyone.
- If the pack depends on an older tModLoader release, pin that release with
tmlversion.txtor the documented version setting instead of allowing an automatic upgrade.
Keep a known-good copy until the new combination has loaded the world and completed a save. Never overwrite your only backup during an update.
Backups and recovery
Back up the world before adding a large content mod, changing tModLoader versions, or editing server configuration. A useful backup set contains the .wld file, serverconfig.txt, the Mods directory or its reproducible Workshop manifests, and a note of the tModLoader version.
- Stop the server before copying a world so the backup is not taken during a save.
- Keep at least one copy outside the server machine or container.
- Label backups with the date and the mod-pack or tModLoader version.
- To recover from a failed update, stop the service, restore the last known-good world and configuration, pin the compatible version, and update every client to that same state.
Troubleshoot common failures
| Symptom | What to check | Corrective action |
|---|---|---|
| Server starts vanilla or Calamity content is missing | The process may be Terraria’s vanilla executable; Calamity may be absent from enabled.json; install.txt may be missing. |
Launch the tModLoader server, restore both pack files to the Mods directory, and verify that Calamity is enabled. |
| “Mods not matching” or join failure | Compare enabled lists, mod versions, tModLoader versions, install.txt, and enabled.json on every client and the server. |
Recreate the pack from the authoritative client and apply it to all participants, then restart tModLoader. |
| Friends cannot connect from outside the LAN | Check that the process is running, the host firewall allows the selected port, the router forwards it to the correct machine, and players use the current public address. | Correct the rule or address and test again from a genuinely external network. |
| Server crashes after an update | A tModLoader or mod version may no longer match the world or another mod. | Restore the last known-good versions, pin the required tModLoader release, and update server and clients together. |
| Calamity settings appear unchanged | Changes made in server configuration may not be applied while Terraria is still running. | Fully quit Terraria and restart it, then load the server again. |
| World disappears after a container rebuild | The world was stored only inside the disposable container layer. | Mount a persistent world directory and restore the latest external backup. |
Operating-system and architecture notes
tModLoader provides client support for Windows, macOS, and Linux, and the dedicated-server documentation describes Linux and Docker paths. Official utilities currently state that ARM support does not exist for tModLoader or its dedicated server. An ARM VPS, single-board computer, or ARM container host should therefore be treated as incompatible unless the official status changes.
Choose a machine with reliable storage and a stable network connection. Because no authoritative Calamity-specific RAM or bandwidth figure is established, monitor the actual server process, save times, and connection quality as your player count and mod list grow rather than relying on an invented specification.
Practical security and administration
- Use a password for private worlds and share it only with the intended players.
- Run the server under a restricted user account where your operating system supports that arrangement.
- Expose only the game port you need; do not broadly disable the host firewall.
- Keep the operating system, tModLoader, and deployment tools updated, but stage mod updates with a backup and a rollback plan.
- Document the world path, Mods path, port, password-rotation procedure, and the exact command used to start the service.
- Decide who can restart the service and restore backups before the original host goes offline.
Which setup should you use?
For two or three friends who play together, use Host & Play and a saved mod pack. For a world that should remain available, deploy a dedicated tModLoader server with the management script or Docker, then automate or document restarts and backups. Choose Docker when isolation and repeatable deployment matter most; choose the management script when direct filesystem control and a conventional server process are more important. Use managed hosting only after confirming current tModLoader support, mod-folder access, backup options, location, limits, and pricing.
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