lliquidlink 1.2.0

A bridge library for operating Unity Editor features from an external Python process via JSON-RPC.

日本語

python

cube = client.GameObject.CreatePrimitive(enum("Cube"))
cube.transform.Rotate(30, 45, 0)

To Unity

LLiquidLink / UniLiquidLink

A bridge library for operating Unity Editor features from an external Python process via JSON-RPC. It lets you call Unity from Python using almost the same syntax as Unity C#.

Features

• Write with almost the same syntax as Unity C#
  • C#: cube.transform.Rotate(30, 45, 0) Python: cube.transform.Rotate(30, 45, 0)
  • Property chains and method calls are converted as-is
• Runs from Python with no compilation and no types
  • The compilation and type declarations required in C# are not needed in Python
• Unity and Python are completely independent Unity (C#) and Python are separate processes that communicate only via JSON-RPC. Since they have no direct bindings or DLL dependencies on each other, they work with any combination of Unity version and Python version the user chooses.
• Only functionality registered on the C# side can be executed From Python you can only call methods/properties that were explicitly registered on the C# side. Unregistered APIs cannot be called at all (whitelist approach)
• Built on anyio, supporting a wide range of transport layers The core communication layer (lliquidlink.core / lliquidlink.client) is implemented on top of anyio. Currently only TCP and stdio are supported, but the design allows extension via anyio.

Architecture

A 3-process configuration consisting of the Python "user client", the "middleware", and the Unity "C# server".

flowchart LR
    subgraph SG1["User Python Process"]
        PythonClient["lliquidlink.client"]
    end
    subgraph SG2["Python Middleware Process"]
        PythonServer["lliquidlink.server"]
    end
    subgraph SG3["Unity Editor Process (C#)"]
        Sharp["UniLiquidLink.Server"]
    end
    PythonClient <-->|tcp| PythonServer
    PythonServer <-->|stdio| Sharp

Installation

Unity (C#) side

1. In Unity, open Window > Package Manager > + > Add package from git URL... and enter:

   https://github.com/hide00310/UniLiquidLink.git
   

   (Replace the tag with the latest released version. It is treated as an Editor-only assembly via UniLiquidLink.asmdef.)

2. UniLiquidLink.asmdef references the following precompiled DLL. If this is not present in your project, you will get a compile error.

   • System.Text.Json.dll

   Example ways to obtain it:

   • Get the NuGet package (System.Text.Json) via NuGetForUnity or similar, and place the DLL under Assets/Plugins etc.
   • Since these are only needed in the Editor, it is recommended to set the target platform to Editor only in the Plugins Inspector

Python side

pip install lliquidlink

How to run

You can verify it works using the UniLiquidLink Samples sample, which bundles Cube Demo and All Features Tour in a single window. In Window > Package Manager, select the UniLiquidLink package, open the Samples tab, and click Import next to UniLiquidLink Samples. It is copied into Assets/Samples/UniLiquidLink/<version>/UniLiquidLinkSample/.

1. Run UniLiquidLink/Samples/Sample Window from the Unity menu, pick Cube Demo, and press Start — no command needs to be entered: the Python command defaults to python and the middleware script path is resolved automatically. Start the server on the C# side (it listens on http://localhost:8700 by default).

// CubeDemoServer.cs (excerpt)
server = new Server();
server.RegisterCallerAssembly();

// Create a primitive: client.GameObject.CreatePrimitive(enum("Cube"))
server.Rpc.AddRpcMethod((Func<PrimitiveType, GameObject>)GameObject.CreatePrimitive);

// Property chain: cube.transform.Rotate(...) or cube.transform.position = ...
server.Rpc.AddRpcGetProperty((GameObject obj) => obj.transform);

2. Run the sample script on the Python side.

python Assets/Samples/UniLiquidLink/<version>/UniLiquidLinkSample/CubeDemo/create_and_rotate_cube.py

# create_and_rotate_cube.py (excerpt)
from lliquidlink.client import Client, TcpJsonRpcTransport
from lliquidlink.client.models import type_, enum

def on_execute(client):
    cube = client.GameObject.CreatePrimitive(enum("Cube"))
    renderer = cube.GetComponent(type_("Renderer"))
    renderer.material.color = {"r": 1, "g": 0, "b": 0, "a": 1}
    cube.transform.Rotate(30, 45, 0)

client = Client(TcpJsonRpcTransport("localhost", 8700))
client.on_execute += on_execute
client.mainloop()

When run, a red Cube is created in the Unity scene and rotates.

Supported features

• RPC method registration (C# side)
  • Register static/instance methods individually
  • Register property getters/setters individually
• Bulk RPC method registration (C# side)
  • Register all public methods/properties of a class at once
• Passing instance objects Instance objects such as Unity's GameObject can be passed back and forth on the Python side
• Type/Enum resolution Resolves Unity types by name, such as type_("Renderer") or enum("Cube")
• Serialization Mainly uses System.Text.Json, while Unity-specific value types such as Vector3 are converted using JsonUtility-based serialization
• Method overload support
  • If a registered method has overloads, they are resolved in order and the one that succeeds is used

Security notes

• This library implements no authentication or authorization mechanism whatsoever. The HTTP server (by default localhost:8700) unconditionally accepts any client that connects.
• The only real protective boundary is that it binds to localhost only by default. If you configure it to be exposed to a LAN or the internet, add a reverse proxy, VPN, or token authentication/TLS termination via a transport-layer subclass, etc.
• The whitelist approach — where only RPCs explicitly registered on the C# side can be executed — is the only execution control in place, but note that if you bulk-register an entire class with AddRpcAllMethod, a wider API surface than intended may become externally callable.
• Arbitrary registered C# code executes with the same privileges as the Unity Editor process, so do not start this server on an untrusted network.

Development

The following are additionally required only if you want to run the tests.

pip install pytest pytest-asyncio

Verified tool versions

The following are combinations that have been developed and verified to work (not strict required versions).

Tool / Library	Version
Unity Editor	2022.3.22f1 (Editor only)
Python	3.13.11
anyio	4.14.1
pytest (for testing)	9.0.3
pytest-asyncio (for testing)	1.3.0