René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"FastMCP server with SSE transport fails to shut down on a signal","articleBody":"A very simple server fails to shut down on a signal if it processed at least one request:\n\n```\n❯ python test-server.py --port=8085\nINFO:     Started server process [216035]\nINFO:     Waiting for application startup.\nINFO:     Application startup complete.\nINFO:     Uvicorn running on http://0.0.0.0:8085 (Press CTRL+C to quit)\nINFO:     127.0.0.1:55188 - \"GET /sse HTTP/1.1\" 200 OK\nINFO:     127.0.0.1:55192 - \"POST /messages/?session_id=e690de9733914d09aebf2b0e8c78191c HTTP/1.1\" 202 Accepted\nINFO:     127.0.0.1:55192 - \"POST /messages/?session_id=e690de9733914d09aebf2b0e8c78191c HTTP/1.1\" 202 Accepted\nINFO:     127.0.0.1:55192 - \"POST /messages/?session_id=e690de9733914d09aebf2b0e8c78191c HTTP/1.1\" 202 Accepted\nProcessing request of type CallToolRequest\n^CINFO:     Shutting down\nINFO:     Waiting for background tasks to complete. (CTRL+C to force quit)\n```\n\nThe expected behaviour would be:\n\n```\n❯ python test-server.py --port=8085\nINFO:     Started server process [216006]\nINFO:     Waiting for application startup.\nINFO:     Application startup complete.\nINFO:     Uvicorn running on http://0.0.0.0:8085 (Press CTRL+C to quit)\n^CINFO:     Shutting down\nINFO:     Waiting for application shutdown.\nINFO:     Application shutdown complete.\nINFO:     Finished server process [216006]\n```\n\nHere is the code for both the server and the client.\n\nWhat do I miss?\n\nthe server\n\n```\nimport click\nimport sys\nfrom pydantic import Field\nfrom mcp.server.fastmcp import FastMCP\n\n@click.command()\n@click.option(\"--port\", default=8085, help=\"Port to listen\", type=int)\ndef main(port: int):\n    mcp = FastMCP(\n        \"mcp-echo-tool\",\n        debug=True,\n        log_level=\"INFO\",\n        port=port,\n    )\n\n    @mcp.tool(name=\"echo\")\n    async def echo_tool(string: str = Field(description=\"A string to echo back\")) -\u003e str:\n        \"\"\"Echoes back the input string\"\"\"\n        return string\n\n    mcp.run(transport='sse')\n    return 0\n\nif __name__ == \"__main__\":\n    sys.exit(main())\n```\n\nand the client\n\n```\nimport asyncio\nimport click\nimport sys\nfrom mcp.client.session import ClientSession\nfrom mcp.client.sse import sse_client\n\nasync def client(url, string):\n    async with sse_client(url) as (read, write):\n        async with ClientSession(read, write) as session:\n            await session.initialize()\n            result = await session.call_tool(\"echo\", {\"string\": string})\n            print(result.content)\n\n@click.command()\n@click.option('--url', default='http://localhost:8085', help='MCP Server URL', type=str)\n@click.argument('string', type=str)\ndef main(url: str, string: str):\n    asyncio.run(client(url, string))\n\nif __name__ == \"__main__\":\n    sys.exit(main())\n```\n\n","author":{"url":"https://github.com/growler","@type":"Person","name":"growler"},"datePublished":"2025-04-14T21:46:41.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/514/python-sdk/issues/514"}