Run a server and join it

On this page you start a server on your own machine, join it with a vanilla client and see what you can do there. You need the tools from Install the tools first.

WIP

A detailed guide will come before the alpha. This page copies the commands of the README Quick start, and we have not run them again for the docs. If the README and this page differ, trust the README.

Do not open the port to the internet

The server has no authentication, so anyone who reaches it can join under any name, including the name of an operator. It listens on all network interfaces (0.0.0.0:25565). Run it only on your own machine or on a trusted local network.

Start the server

cargo run --release
cargo run --release -- "<path to a world folder>"

The first command starts a server on a new world. The second one opens an existing Java Edition save, which must have the same data version as the game snapshot (26.4-snapshot-7). Saves of other versions do not load, and there are no datafixers.¹

On the reference machine, an Apple M4 Max with macOS, a release build with no world folder reaches the Playing state in 0.77 s, the median of three runs. This is the start time of a binary that is already built, so it does not include the build. The measurement is in PERF.md.

Join with a vanilla client

Use a vanilla client of the same snapshot, 26.4-snapshot-7. The server announces itself in the LAN worlds list, and you can also join by the address localhost:25565. The server runs in offline mode.

What you can do

• Write in chat.
• Run commands from the client or from the server console, which reads standard input: /gamemode, /tp, /summon pig, /time, /fill.
• Break blocks in creative mode. The default game mode is creative.
• Fly around the generated world and spawn mobs with /summon: pigs, cows, sheep, chickens and zombified piglins.

The server reads its settings from environment variables, for example MCRS_PORT, MCRS_WORLD_SEED, MCRS_WORLD_PRESET (normal or flat) and MCRS_DEFAULT_GAMEMODE. The full list is in server_settings.rs.

Blocks you change are not saved

The server does not write changed chunks to disk, so every block you break is lost when the server stops.² Players are saved on a clean shutdown.³ A clean shutdown does not save the world yet.⁴

The expected console output and a first-run checklist are not written yet. For those details, read the README.

Footnotes

1. Not planned#388 The decision that saves are read at exactly the targeted data version, with no datafixers. ↩

2. WIP#78 Tracks saving changed chunks back to region files. ↩

3. Works#624 The server disconnects and saves every player before a shutdown exits. ↩

4. WIP#169 Tracks a clean shutdown that saves players and the world. ↩