Cobble

Cobble builds a modded Minecraft world for you and your friends. It checks every mod it downloads, then starts the server and waits until the world answers. Only then does it say ready.

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What it does

  1. Finds mods

    Searches for mods that match your version and loader, and tells you where each one came from.

  2. Builds the pack

    Downloads them and checks every file against the hash the source published. A file that does not match is not used.

  3. Asks the world

    Starts the server and waits until it answers a real ping. Only then does it say the world is ready.

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Server runner

cobbled is the whole product without a window. It builds a pack, boots the server, and tells you whether a player could actually join. It needs Java 21 and nothing else. 

# macOS and Linux. Use the archive for your own platform.
tar -xzf cobbled-<target>.tar.gz
./cobbled search 1.21.1 fabric performance --oss
./cobbled build ./server 1.21.1 fabric @performance
./cobbled verify 127.0.0.1 25565 240
# the verifier answers one question honestly: can a player join?
{"ok":true,"host":"127.0.0.1","port":25565,"ready_ms":4634,"motd":"cobble fabric fixture"}

A successful TCP connection is not proof. In this project's own measurements a dial succeeded at 0 ms on every run, while the server needed another 5 to 13 seconds before it could answer a ping. A verifier that trusts a dial reports success at the exact moment a player would be dropped.