MultiLogin Compat Mod

mc-multilogin-compat-mod

A Fabric server-side mod for Minecraft 1.21.1 (Mojang mappings) that integrates with 1.21.1.

一个用于 Minecraft 1.21.1（Mojang 映射表）的 Fabric 服务端模组，用于与 MC-MultiLogin-service 集成，可以实现多源登录方式。

We suggest you to use this with Authlib-Injector. This mod only change the login method and the login-failed message.

建议配合 Authlib-Injector 使用。此模组仅修改登录方式和登录失败时的提示信息。如果您使用`Authlib-Injector`，请记得设定它的链接为 `MC-MultiLogin-service`提供的API地址。

Velocity Plugin Version

Config can be found at `pluginsmultilogin-auth-compatmultilogin-compat-config.json`.

配置可以在`pluginsmultilogin-auth-compatmultilogin-compat-config.json`找到。

Fabric Mod Version

Features

- On every player login the mod calls the configured MC-MultiLogin-service endpoint with `detail=true`, so authentication failures return a structured JSON error instead of the generic "Failed to verify username!" message. - Detailed error reasons (`DUPLICATE_NAME`, `BANNED`, `NOT_FOUND`, …) are forwarded directly to the connecting client in the disconnect screen. - Auto-rename on `DUPLICATE_NAME` (configurable): when the service reports that a player name is already taken by another skin-site account, the mod automatically retries the login with the service-suggested `availableId` (e.g. `Steve_2`) and records the original → new-name mapping in `config/mc-multilogin-renames.json`.

Setup

1. Place the mod JAR in your server's `mods/` directory. 2. Start the server once – a default config file will be generated at `config/mc-multilogin-compat.json` and the server will stop with an error asking you to fill in the API URL. 3. Edit the config and set `apiUrl` to the base URL of your MC-MultiLogin-service method entry (e.g. `http://127.0.0.1:25600/login/my`). 4. Restart the server.

Configuration (`config/mc-multilogin-compat.json`)

```json { "apiUrl": "http://127.0.0.1:25600/login/my", "autoRename": true } ```

| Field | Type | Default | Description | |-------------|---------|---------|-------------| | `apiUrl` | string | `""` | Required. Base URL of the MC-MultiLogin-service login method (e.g. the path configured under `method[].url`). The mod appends `/session/minecraft/hasJoined?…` automatically. | | `autoRename`| boolean | `true` | (Not working at present) When `true`, a `DUPLICATE_NAME` rejection triggers an automatic retry using the `availableId` returned by the service. The rename is persisted in `config/mc-multilogin-renames.json`. Set to `false` to disable and show the error instead. |

Building

```bash

Requires Java 21 and internet access to maven.fabricmc.net

./gradlew build ```

The output JAR will be in `build/libs/`.