89 lines
3.2 KiB
Python
89 lines
3.2 KiB
Python
"""
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Stdio Server Transport Module
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This module provides functionality for creating an stdio-based transport layer
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that can be used to communicate with an MCP client through standard input/output
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streams.
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Example usage:
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```
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async def run_server():
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async with stdio_server() as (read_stream, write_stream):
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# read_stream contains incoming JSONRPCMessages from stdin
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# write_stream allows sending JSONRPCMessages to stdout
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server = await create_my_server()
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await server.run(read_stream, write_stream, init_options)
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anyio.run(run_server)
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```
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"""
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import sys
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from contextlib import asynccontextmanager
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from io import TextIOWrapper
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import anyio
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import anyio.lowlevel
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from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
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import mcp.types as types
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from mcp.shared.message import SessionMessage
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@asynccontextmanager
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async def stdio_server(
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stdin: anyio.AsyncFile[str] | None = None,
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stdout: anyio.AsyncFile[str] | None = None,
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):
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"""
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Server transport for stdio: this communicates with an MCP client by reading
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from the current process' stdin and writing to stdout.
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"""
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# Purposely not using context managers for these, as we don't want to close
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# standard process handles. Encoding of stdin/stdout as text streams on
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# python is platform-dependent (Windows is particularly problematic), so we
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# re-wrap the underlying binary stream to ensure UTF-8.
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if not stdin:
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stdin = anyio.wrap_file(TextIOWrapper(sys.stdin.buffer, encoding="utf-8"))
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if not stdout:
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stdout = anyio.wrap_file(TextIOWrapper(sys.stdout.buffer, encoding="utf-8"))
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read_stream: MemoryObjectReceiveStream[SessionMessage | Exception]
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read_stream_writer: MemoryObjectSendStream[SessionMessage | Exception]
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write_stream: MemoryObjectSendStream[SessionMessage]
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write_stream_reader: MemoryObjectReceiveStream[SessionMessage]
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read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
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write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
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async def stdin_reader():
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try:
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async with read_stream_writer:
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async for line in stdin:
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try:
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message = types.JSONRPCMessage.model_validate_json(line)
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except Exception as exc:
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await read_stream_writer.send(exc)
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continue
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session_message = SessionMessage(message)
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await read_stream_writer.send(session_message)
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except anyio.ClosedResourceError:
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await anyio.lowlevel.checkpoint()
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async def stdout_writer():
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try:
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async with write_stream_reader:
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async for session_message in write_stream_reader:
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json = session_message.message.model_dump_json(by_alias=True, exclude_none=True)
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await stdout.write(json + "\n")
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await stdout.flush()
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except anyio.ClosedResourceError:
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await anyio.lowlevel.checkpoint()
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async with anyio.create_task_group() as tg:
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tg.start_soon(stdin_reader)
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tg.start_soon(stdout_writer)
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yield read_stream, write_stream
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