René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Proactor Windows warning on cleanup when using stdio_client","articleBody":"**Describe the bug**  \nWhen connecting to a sdio MCP server on Windows, a warning is printed during the final cleanup. This does not crash the program but indicates that there might be a need for a more graceful shutdown of subprocess transports.\n\n**To Reproduce**  \nRun the following script:\n   ```python\n   import asyncio\n\n   from mcp import ClientSession, StdioServerParameters, stdio_client\n\n\n   async def main():\n       server_params = StdioServerParameters(\n           command=\"npx\", args=[\"-y\", \"@playwright/mcp@latest\"]\n       ) # Or any other server\n\n       async with stdio_client(server_params) as (read, write):\n           async with ClientSession(read, write) as session:\n               await session.initialize()\n               print(await session.list_tools())\n               await asyncio.sleep(2.0)\n\n\n   if __name__ == \"__main__\":\n       asyncio.run(main())\n   ```\nRunning the above, we get a bunch of warnings and error messages at the end:\n   ```\n   Exception ignored in: \u003cfunction BaseSubprocessTransport.__del__ at 0x...\u003e\n   Traceback (most recent call last):\n     ...\n   ValueError: I/O operation on closed pipe\n   ```\n\n**Expected behavior**  \nNo warnings or errors should be printed during final cleanup. All subprocess transports and associated resources should be closed cleanly without attempting operations on closed pipes.\n\n**Desktop:**  \n- OS: Windows 10   \n- Version: Python 3.11 (mcp v1.6.0)","author":{"url":"https://github.com/S4mpl3r","@type":"Person","name":"S4mpl3r"},"datePublished":"2025-03-29T12:26:42.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/391/python-sdk/issues/391"}