wehub-resource-sync
228 lines
8.4 KiB
Python
228 lines
8.4 KiB
Python
# /// script # noqa: CPY001
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# dependencies = [
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# "semantic-kernel[mcp]",
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# ]
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# ///
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# Copyright (c) Microsoft. All rights reserved.
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import argparse
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import ipaddress
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import logging
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from typing import Any, Literal
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from semantic_kernel import Kernel
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from semantic_kernel.connectors.ai.open_ai import OpenAIChatCompletion
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from semantic_kernel.functions import kernel_function
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from semantic_kernel.prompt_template import PromptTemplateConfig
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from semantic_kernel.prompt_template.input_variable import InputVariable
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logger = logging.getLogger(__name__)
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"""
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This sample demonstrates how to expose your Semantic Kernel `kernel` instance as a MCP server.
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To run this sample, set up your MCP host (like Claude Desktop or VSCode Github Copilot Agents)
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with the following configuration:
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```json
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{
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"mcpServers": {
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"sk": {
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"command": "uv",
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"args": [
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"--directory=<path to sk project>/semantic-kernel/python/samples/demos/mcp_server",
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"run",
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"sk_mcp_server.py"
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],
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"env": {
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"OPENAI_API_KEY": "<your_openai_api_key>",
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"OPENAI_CHAT_MODEL_ID": "gpt-4o-mini"
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}
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}
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}
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}
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```
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Note: You might need to set the uv to its full path.
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Alternatively, you can run this as a SSE server, by setting the same environment variables as above,
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and running the following command:
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```bash
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uv --directory=<path to sk project>/semantic-kernel/python/samples/demos/mcp_server \
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run sk_mcp_server.py --transport sse --port 8000
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```
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This will start a server that listens for incoming requests on port 8000.
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In both cases, uv will make sure to install semantic-kernel with the mcp extra for you in a temporary venv.
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"""
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def is_loopback_host(host: str) -> bool:
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"""Return True if the host refers to a loopback interface (incl. IPv6 ::1)."""
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if host == "localhost":
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return True
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try:
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return ipaddress.ip_address(host).is_loopback
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except ValueError:
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return False
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def parse_arguments():
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parser = argparse.ArgumentParser(description="Run the Semantic Kernel MCP server.")
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parser.add_argument(
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"--transport",
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type=str,
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choices=["sse", "stdio"],
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default="stdio",
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help="Transport method to use (default: stdio).",
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)
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parser.add_argument(
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"--port",
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type=int,
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default=None,
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help="Port to use for SSE transport (required if transport is 'sse').",
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)
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parser.add_argument(
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"--host",
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type=str,
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default="127.0.0.1",
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help=(
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"Host/interface to bind the SSE server to (default: 127.0.0.1). "
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"Binding to anything other than loopback (e.g. 0.0.0.0) exposes the server "
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"to the network and should only be done on a trusted network with authentication added."
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),
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)
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args = parser.parse_args()
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if args.transport == "sse" and args.port is None:
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parser.error("--port is required when --transport is 'sse'.")
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return args
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def run(transport: Literal["sse", "stdio"] = "stdio", port: int | None = None, host: str = "127.0.0.1") -> None:
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kernel = Kernel()
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@kernel_function()
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def echo_function(message: str, extra: str = "") -> str:
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"""Echo a message as a function"""
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return f"Function echo: {message} {extra}"
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kernel.add_service(OpenAIChatCompletion(service_id="default"))
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kernel.add_function("echo", echo_function, "echo_function")
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kernel.add_function(
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plugin_name="prompt",
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function_name="prompt",
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prompt_template_config=PromptTemplateConfig(
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name="prompt",
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description="This is a prompt",
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template="Please repeat this: {{$message}} and this: {{$extra}}",
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input_variables=[
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InputVariable(
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name="message",
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description="This is the message.",
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is_required=True,
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json_schema='{ "type": "string", "description": "This is the message."}',
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),
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InputVariable(
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name="extra",
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description="This is extra.",
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default="default",
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is_required=False,
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json_schema='{ "type": "string", "description": "This is the message."}',
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),
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],
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),
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)
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server = kernel.as_mcp_server(server_name="sk")
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if transport == "sse" and port is not None:
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import uvicorn
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from mcp.server.sse import SseServerTransport
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from starlette.applications import Starlette
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from starlette.middleware import Middleware
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from starlette.middleware.trustedhost import TrustedHostMiddleware
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from starlette.responses import PlainTextResponse
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from starlette.routing import Mount, Route
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from starlette.types import ASGIApp, Receive, Scope, Send
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# A local MCP server is a security boundary, not a generic web server: it exposes
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# tools, plugins and model providers backed by the developer's credentials. Without
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# Host/Origin validation a malicious web page could use DNS rebinding to reach this
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# loopback listener from the victim's browser and invoke the exposed MCP tools.
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# The MCP spec therefore requires servers to validate Origin and bind to loopback.
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allowed_hosts = [
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"localhost",
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"127.0.0.1",
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"[::1]",
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f"localhost:{port}",
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f"127.0.0.1:{port}",
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f"[::1]:{port}",
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]
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allowed_origins = {
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"http://localhost",
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"http://127.0.0.1",
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"http://[::1]",
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f"http://localhost:{port}",
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f"http://127.0.0.1:{port}",
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f"http://[::1]:{port}",
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}
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class OriginValidationMiddleware:
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"""Reject requests with an untrusted Origin header (DNS-rebinding defense)."""
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def __init__(self, app: ASGIApp) -> None:
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self.app = app
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async def __call__(self, scope: Scope, receive: Receive, send: Send) -> None:
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if scope["type"] == "http":
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origin = dict(scope["headers"]).get(b"origin")
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if origin is not None:
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try:
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origin_value = origin.decode("ascii")
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except UnicodeDecodeError:
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origin_value = None
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if origin_value not in allowed_origins:
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response = PlainTextResponse("Forbidden: invalid Origin header", status_code=403)
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await response(scope, receive, send)
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return
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await self.app(scope, receive, send)
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sse = SseServerTransport("/messages/")
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async def handle_sse(request):
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async with sse.connect_sse(request.scope, request.receive, request._send) as (read_stream, write_stream):
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await server.run(read_stream, write_stream, server.create_initialization_options())
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starlette_app = Starlette(
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debug=False,
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routes=[
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Route("/sse", endpoint=handle_sse),
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Mount("/messages/", app=sse.handle_post_message),
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],
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middleware=[
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Middleware(TrustedHostMiddleware, allowed_hosts=allowed_hosts),
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Middleware(OriginValidationMiddleware),
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],
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)
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if not is_loopback_host(host):
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logger.warning(
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"Binding the MCP SSE server to %s exposes it beyond loopback. The bundled Host/Origin "
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"checks only allow loopback callers; for a network-reachable or credentialed deployment "
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"add proper authentication (see the mcp_with_oauth sample) before doing this.",
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host,
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)
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uvicorn.run(starlette_app, host=host, port=port) # nosec
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elif transport == "stdio":
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import anyio
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from mcp.server.stdio import stdio_server
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async def handle_stdin(stdin: Any | None = None, stdout: Any | None = None) -> None:
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async with stdio_server() as (read_stream, write_stream):
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await server.run(read_stream, write_stream, server.create_initialization_options())
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anyio.run(handle_stdin)
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if __name__ == "__main__":
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args = parse_arguments()
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run(transport=args.transport, port=args.port, host=args.host)
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