A .NET client library for the original (Java) version of Minecraft. It requires Forge and the Raspberry Jam mod on the Minecraft side.

Requirements: Minecraft (the Java version, not the micro edition or the Windows 10 edition), Forge, and the Raspberry Jam Mod].

Reference the library, then you can open a connection and start scripting the Minecraft world:

using (var world = JavaWorld.Connect())
{
    world.PostToChat("Hello from C# and .NET Core!");
    var originBlock = world.GetBlockType(0, 0, 0);
    world.PostToChat($"Origin block is {originBlock}.");
}

This is just a hack at this point: only a minimal number of APIs is implemented, but the general infrastructure is in place, and the code can actually script Minecraft from C#, which is pretty awesome in itself.

There's a Minecraft mod that enables scripting Minecraft in Python called Raspberry Jam Mod. The way that mod works is with a small Java mod that lives in Minecraft, accepting socket connections from a Python client and then exchanging text-based messages that on the wire look like function calls:

world.getBlock(1,0,0)

The interesting thing is that there is nothing specific about Python in that protocol: it's just messages getting exchanged over a socket, which .NET will be happy to emulate.

What I did is to reverse-engineer the Python client code and re-implement it in C#.

Eventually, I'd like to expose the entire Minecraft API with a nice object model, and to be able to start the C# scripts from the Minecraft console. That would effectively make it possible to write mods in C#, with a thin Java driver.

CSX support would be nice as well.

I also want to be able to run this with Mono (that should actually already work, this is just .NET Standard) on a Raspberry Pi: the protocol that Raspberry Jam implements is natively present on the Raspberry Pi version.

The project must now be built with csproj-based tooling (Visual Studio 2017 with Core tooling or .NET Core CLI Preview 3 or later).

Sure. Just let me know what you'd like to work on, so we don't duplicate efforts, but yes, hacking is highly encouraged.

This is an easy contribution.

There's a couple hundred blocks to implement. Some of them, such as Diamond, are very simple, and some are a little more complex, such as Fire. In some cases, such as Clay, a class hierarchy makes sense.

If you're interested in implementing blocks, look at the existing blocks in the Blocks folder, then choose one from the BlockType enum that doesn't exist yet and implement it. A block is a class that derives from Block. In the simplest case, the class is empty:

public class Diamond : IBlock {}

The block class is only part of the implementation, that is supposed to be a simple data structure with no knowledge of the communication protocol with Minecraft. The code that does know about the protocol must be implemented in JavaBlock, in the JavaBlock static constructor, and in the public static JavaBlock From(Block block) method.

The static constructor describes how to instantiate the correct block type from data that was passed in. In simple cases, there is no data, and no need to implement construction logic.

When blocks have data, the block contruction logic must build the correct block from the wire data:

_ctors[Id<Farmland>()] = d => new Farmland(d);

In more complex cases, the data must be decomposed and the corresponding properties must be set on the block object.

The reverse operation implemented in the From method is recreating a JavaBlock ready to be transmitted to Minecraft from a concrete block. If the block you're implementing has no data, nothing has to be implemented, and this part can be skipped.

The description of the format of the data for each block type that has data can be found in The Minecraft documentation wiki Data values page.

Entities will be an easy contribution once I've started creating the basic infrastructure.

This is an easy to medium contribution.

There are lots of blocks that need testing of their serialization and deserialization logic. We also need tests for infrastructure pieces such as JavaWorld. Finally, we'll ultimately need functional tests.

This is a medium difficulty contribution.

Very few commands are currently implemented: you can echo messages to the chat using PostToChat, you can get the position of the player using Player.GetPosition, and you can get or set a block using GetBlock and SetBlock. Many more commands need to be implemented. You can find the list of commands and their Python implementation in the Raspberry Jam Mod GitHub repository. Make sure you implement both an asynchronous and a synchronous version of each method. Finally, once you've implemented a command, don't forget to add it to the IWorld interface.

This is a difficult contribution.

Currently, this library can only talk to the Java implementation of Minecraft, and to the Raspberry Pi version (hopefully, I haven't verified it yet). The code is architected so that it should be possible to implement alternative protocols by reimplementing JavaConnection, JavaWorld, and JavaBlock. This way, a single API could in theory be used to script other versions of the Minecraft client and of Minecraft servers.

It is useful, while developing scripts, to be able to switch to another application without the game going into pause. This can be done by editing the options.txt file under your Minecraft folder (%appdata%\.minecraft\ on Windows, ~/Library/Application Support/minecraft/ on macOS, and ~/.minecraft/ on Linux) and setting pauseOnLostFocus to false.