created

Author: Richard Lack

.gitignore

@@ -135,6 +135,7 @@ venv/
 ENV/
 env.bak/
 venv.bak/
+venv-*
 
 # Spyder project settings
 .spyderproject

DOCKERFILE

@@ -0,0 +1,42 @@
+# Use Ubuntu as the base image
+FROM ubuntu:22.04
+
+# Set non-interactive mode during build
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Update and install Python 3.10 and essential dependencies
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends \
+    python3.10 \
+    python3-pip \
+    python3.10-dev \
+    && ln -sf /usr/bin/python3.10 /usr/bin/python \
+    && ln -sf /usr/bin/python3.10 /usr/bin/python3 \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
+
+# Verify Python version
+RUN python --version
+
+# Create directory for volume mounting
+RUN mkdir -p /usr/code
+
+# Set the working directory
+WORKDIR /usr/code
+
+# Volume configuration for code mounting
+VOLUME ["/usr/code"]
+
+# Default command to run when the container starts
+CMD ["bash"]
+
+
+#--- Build instructions, podman or docker:
+# podman build --tag linux-lab-08b --file DOCKERFILE .
+
+#--- Run instructions
+# Run the following with podman or docker, replacing "your-src-path" with the path to your src/:
+# podman run -it --rm -v "your-src-path:/usr/code" linux-lab-08b bash
+# Then from the vm:
+# cd /usr/code
+# python mcp_client.py

README.md

@@ -1,2 +1,75 @@
-# mcp-client-python-issue
-Repo to diagnose an issue we're having with mcp python client
+# MCP SDK Client Python Issue
+
+This repo is to demonstrate and diagnose an issue we're having with the Python MCP stdio
+client. What happens is it never finishes initializes the server. What I expect to
+happen is for it to initialize the server successfully so that we can start
+communicating with it.
+
+I have tried this in many configurations, including Python 3.10 windows,
+Python 3.12 windows, Python 3.12 under WSL, and running Linux in a container,
+using the latest main branch and also the latest releases,
+and various forms of UV and global Python installations.  I have also tried
+it using `asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())`
+in various Windows configurations.  Under some configurations this leads
+to a new `NotImplementedError`, but under no circumstances was I able to make
+it work.
+
+I haven't been able to make a Python client work yet.  I can get node client
+and server working without difficulties, though.
+
+## Repro steps, Windows and UV
+From the root directory of the project (above src):
+```Powershell
+uv venv --python=3.10 venv
+.\venv\Scripts\activate.ps1
+uv pip install mcp
+```
+
+Output under windows:
+```
+(venv) PS C:\Users\rilack\code\mcp-client-python-issue\src> python mcp_client.py
+Ultra Basic MCP Client
+sys.executable='C:\\Users\\rilack\\code\\mcp-client-python-issue\\venv\\Scripts\\python.exe'
+Python version 3.10.16 (main, Mar 17 2025, 20:54:03) [MSC v.1943 64 bit (AMD64)]
+Initializing session...
+```
+And that is the last thing that we see.
+
+## Repro steps, Docker, Ubuntu
+To eliminate the variables that this could be an issue with Windows or UV,
+I also tested this with Linux.  I have tried this both with Python 3.12 and 3.10
+with the same results.
+
+### Build container
+I used `podman` to build and run my containers, but you can use `docker` instead.
+
+From the root of the project:
+```bash
+podman build --tag mcp-lab-08c --file DOCKERFILE .
+```
+
+### Run container
+Replace `your-src-path` to the directory of your local machine where this project is installed.
+```bash
+podman run -it --rm -v "your-src-path:/usr/code" mcp-lab-08c bash
+```
+So for me, I used:
+```bash
+podman run -it --rm -v "c:\Users\rilack\code\mcp-client-python-issue:/usr/code" mcp-lab-08c bash
+```
+
+Then from the container:
+```bash
+pip install mcp
+cd src
+python mcp_client.py
+```
+
+Output:
+```
+root@85b6bb0ac0e8:/usr/code/src# python mcp_client.py
+Ultra Basic MCP Client
+sys.executable='/usr/bin/python'
+Python version 3.10.12 (main, Feb  4 2025, 14:57:36) [GCC 11.4.0]
+Initializing session...
+```

src/mcp_client.py

@@ -0,0 +1,57 @@
+import asyncio
+import sys
+
+from mcp import ClientSession, StdioServerParameters, types
+from mcp.client.stdio import stdio_client
+
+# From https://github.com/modelcontextprotocol/python-sdk?tab=readme-ov-file#writing-mcp-clients
+
+
+# Create server parameters for stdio connection
+server_params = StdioServerParameters(
+    command=sys.executable, # Leverage the parent python environment so the child also uses python 3.10 with the same libraries.
+    args=["mcp_echo_server.py"],  # Optional command line arguments
+    env=None,  # Optional environment variables
+)
+
+# Removed the optional sampling callback for simplicity.
+
+async def run():
+    async with stdio_client(server_params) as (read, write):
+        async with ClientSession(read, write) as session:
+            # Initialize the connection
+            print("Initializing session...") # This is the last thing we will see.
+            await session.initialize()
+            print("Session initialized successfully.") # If it's broken we won't see this.
+
+            # List available prompts
+            prompts = await session.list_prompts()
+
+            # Get a prompt
+            prompt = await session.get_prompt(
+                "example-prompt", arguments={"arg1": "value"}
+            )
+
+            # List available resources
+            resources = await session.list_resources()
+
+            # List available tools
+            tools = await session.list_tools()
+
+            # Read a resource
+            content, mime_type = await session.read_resource("file://some/path")
+
+            # Call a tool
+            result = await session.call_tool("tool-name", arguments={"arg1": "value"})
+
+
+def main():
+    print('Ultra Basic MCP Client')
+    print(f'{sys.executable=}')
+    print(f'Python version {sys.version}')
+
+    asyncio.run(run())
+
+
+if __name__ == "__main__":
+    main()

src/mcp_echo_server.py

@@ -0,0 +1,23 @@
+# This is used to test the mcp server
+# from https://github.com/modelcontextprotocol/python-sdk?tab=readme-ov-file#echo-server
+from mcp.server.fastmcp import FastMCP
+
+mcp = FastMCP("Echo")
+
+
+@mcp.resource("echo://{message}")
+def echo_resource(message: str) -> str:
+    """Echo a message as a resource"""
+    return f"Resource echo: {message}"
+
+
+@mcp.tool()
+def echo_tool(message: str) -> str:
+    """Echo a message as a tool"""
+    return f"Tool echo: {message}"
+
+
+@mcp.prompt()
+def echo_prompt(message: str) -> str:
+    """Create an echo prompt"""
+    return f"Please process this message: {message}"