stdio.py•2.89 kB
"""
Stdio Server Transport Module
This module provides functionality for creating an stdio-based transport layer
that can be used to communicate with an MCP client through standard input/output
streams.
Example usage:
```
async def run_server():
async with stdio_server() as (read_stream, write_stream):
# read_stream contains incoming JSONRPCMessages from stdin
# write_stream allows sending JSONRPCMessages to stdout
server = await create_my_server()
await server.run(read_stream, write_stream, init_options)
anyio.run(run_server)
```
"""
import sys
from contextlib import asynccontextmanager
import anyio
import anyio.lowlevel
from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
import mcp.types as types
@asynccontextmanager
async def stdio_server(
stdin: anyio.AsyncFile[str] | None = None,
stdout: anyio.AsyncFile[str] | None = None,
):
"""
Server transport for stdio: this communicates with an MCP client by reading
from the current process' stdin and writing to stdout.
"""
# Purposely not using context managers for these, as we don't want to close
# standard process handles.
if not stdin:
stdin = anyio.wrap_file(sys.stdin)
if not stdout:
stdout = anyio.wrap_file(sys.stdout)
read_stream: MemoryObjectReceiveStream[types.JSONRPCMessage | Exception]
read_stream_writer: MemoryObjectSendStream[types.JSONRPCMessage | Exception]
write_stream: MemoryObjectSendStream[types.JSONRPCMessage]
write_stream_reader: MemoryObjectReceiveStream[types.JSONRPCMessage]
read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
async def stdin_reader():
try:
async with read_stream_writer:
async for line in stdin:
try:
message = types.JSONRPCMessage.model_validate_json(line)
except Exception as exc:
await read_stream_writer.send(exc)
continue
await read_stream_writer.send(message)
except anyio.ClosedResourceError:
await anyio.lowlevel.checkpoint()
async def stdout_writer():
try:
async with write_stream_reader:
async for message in write_stream_reader:
json = message.model_dump_json(by_alias=True, exclude_none=True)
await stdout.write(json + "\n")
await stdout.flush()
except anyio.ClosedResourceError:
await anyio.lowlevel.checkpoint()
async with anyio.create_task_group() as tg:
tg.start_soon(stdin_reader)
tg.start_soon(stdout_writer)
yield read_stream, write_stream