Implement dedicated server support by cuspymd · Pull Request #9 · cuspymd/mcp-server-mod

cuspymd · 2026-02-28T23:34:18Z

This PR adds robust dedicated server support for the MCP mod.

Architecture: Tool calls (execute_commands, get_player_info, etc.) are now abstracted behind interfaces. HTTPMCPServer and IPCServer have been moved to shared source code.
Server Implementation: Created server-side implementations of these interfaces that utilize MinecraftServer and ServerWorld classes without touching MinecraftClient.
Thread Safety: Server operations correctly delegate off the HTTP/IPC worker threads back onto the main MinecraftServer thread using server.submit(...).
Logging & Features: execute_commands accurately captures console output from executed commands.
Documentation: The README.md reflects the changes, explaining the differences between Single Player (Client MCP) and Dedicated Server environments, notably that take_screenshot is unsupported natively on dedicated servers. Configuration file is renamed from mcp-client.json to mcp.json with fallback.

PR created automatically by Jules for task 423232572268798275 started by @cuspymd

- Refactored core logic (HTTPMCPServer, IPCServer, CommandExecutor, etc.) into shared `src/main/java/` and implemented client/server specific interfaces to separate dependencies safely. - Added `MCPServerModServer` entry point for dedicated servers. - Made server tools thread-safe by using `server.submit(() -> ...).get()` for operations mutating the world or executing commands. - Implemented `CommandOutput` interceptor in `ServerCommandExecutor` to retrieve command execution feedback. - Migrated the config file from `mcp-client.json` to `mcp.json` automatically. - Updated the `README.md` to clarify Server vs Client mode differences. Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

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src/server/java/cuspymd/mcp/mod/server/tools/ServerCommandExecutor.java

src/main/java/cuspymd/mcp/mod/server/tools/ServerBlockScanner.java

src/main/resources/fabric.mod.json

- `ServerCommandExecutor` now runs `SafetyValidator` on incoming commands when `validate_safety` is true (the default) to prevent unauthorized/destructive commands via the server console. - `ServerCommandExecutor` now wraps its result in the standard MCP JSON-RPC format via `MCPProtocol.createSuccessResponse()`, ensuring consistency with the client executor and MCP clients. Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

…mappings - Moved `MCPServerModServer` and server tools from `src/server` to `src/main` since there is no `server` sourceSet configured, ensuring they are compiled and packaged into the mod JAR. - Resolved symbol mapping issues with `CommandManager` and `ServerPlayerEntity` for Fabric 1.21.11. - Updated `BlockCompressor` to use a dedicated `BlockData` object to avoid `JsonObject` mapping conflicts across sides. Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

`ServerBlockScanner` now returns a JSON object with an `"error"` property when validation or execution fails (e.g., no online players, area too large). This ensures that `HTTPMCPServer` correctly interprets the failure and wraps it as a proper MCP error response, instead of misclassifying it as a successful result containing an embedded error payload. Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

cuspymd · 2026-03-01T04:49:15Z

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src/main/java/cuspymd/mcp/mod/server/tools/ServerCommandExecutor.java

src/main/java/cuspymd/mcp/mod/server/tools/ServerBlockScanner.java

- Commands executed by the dispatcher now correctly reflect their execution result by assigning `successCount = server.getCommandManager().getDispatcher().execute(...)`. Previously, `successCount` was hardcoded to `1` as long as it didn't throw an exception, resulting in commands with no effect being marked `applied=true`. Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

- Added a separate `appliedCount` integer to track how many commands successfully returned a non-zero side effect from `dispatcher.execute()`. Previously, `appliedCount` was incorrectly set to `acceptedCount`, breaking consistency with the `results[]` array where parsing failures or empty selectors are marked `applied=false` but `accepted=true`. Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

- Updated `ServerBlockScanner` to use `getId().toString()` rather than `getId().getPath()` so that the block `minecraft:stone` is correctly identified rather than just `stone`. This matches the behavior of the client scanner and avoids merging blocks from different namespaces with the same path. Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

src/main/java/cuspymd/mcp/mod/server/tools/ServerBlockScanner.java

Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

cuspymd · 2026-03-02T07:47:12Z

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chatgpt-codex-connector · 2026-03-02T07:53:30Z

src/main/java/cuspymd/mcp/mod/bridge/IPCServer.java

@@ -20,13 +20,13 @@ public class IPCServer {
    private static final Gson GSON = new Gson();
    private static final int IPC_PORT = 25565; // Default port for IPC


Avoid binding IPC listener to the game's default port

IPCServer hardcodes IPC_PORT to 25565, and this commit now starts that listener on dedicated servers when non-HTTP transport is selected. On servers using the normal gameplay port, this creates a bind collision and MCP fails to start for that transport mode. Make the IPC port configurable (or otherwise distinct from the gameplay listener) so dedicated deployments can actually use IPC mode.

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src/main/java/cuspymd/mcp/mod/server/tools/ServerBlockScanner.java

If a dedicated server runs headless automation via MCP, `get_blocks_in_area` should still function even if the server is completely idle (0 players online). Instead of returning an error, it now falls back to scanning the server's Overworld dimension (`server.getOverworld()`). Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

chatgpt-codex-connector bot reviewed Feb 28, 2026

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google-labs-jules bot and others added 3 commits February 28, 2026 23:59

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google-labs-jules bot and others added 3 commits March 1, 2026 06:40

cuspymd commented Mar 1, 2026

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src/main/java/cuspymd/mcp/mod/server/tools/ServerBlockScanner.java Show resolved Hide resolved

google-labs-jules bot and others added 2 commits March 1, 2026 11:11

Empty commit for comment resolution

6fc6d65

Co-authored-by: cuspymd <8870299+cuspymd@users.noreply.github.com>

Fix server MCP tool exposure and runServer dev setup

e19c24a

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cuspymd merged commit 50ea637 into main Mar 2, 2026
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cuspymd deleted the feature/dedicated-server-support-423232572268798275 branch March 2, 2026 08:35

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Implement dedicated server support#9

Implement dedicated server support#9
cuspymd merged 10 commits intomainfrom
feature/dedicated-server-support-423232572268798275

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		@@ -20,13 +20,13 @@ public class IPCServer {
		private static final Gson GSON = new Gson();
		private static final int IPC_PORT = 25565; // Default port for IPC

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