Files
mcp-python-sdk/src/mcp/server/websocket.py
2025-06-11 11:45:50 +02:00

63 lines
2.3 KiB
Python

import logging
from contextlib import asynccontextmanager
import anyio
from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
from pydantic_core import ValidationError
from starlette.types import Receive, Scope, Send
from starlette.websockets import WebSocket
import mcp.types as types
from mcp.shared.message import SessionMessage
logger = logging.getLogger(__name__)
@asynccontextmanager
async def websocket_server(scope: Scope, receive: Receive, send: Send):
"""
WebSocket server transport for MCP. This is an ASGI application, suitable to be
used with a framework like Starlette and a server like Hypercorn.
"""
websocket = WebSocket(scope, receive, send)
await websocket.accept(subprotocol="mcp")
read_stream: MemoryObjectReceiveStream[SessionMessage | Exception]
read_stream_writer: MemoryObjectSendStream[SessionMessage | Exception]
write_stream: MemoryObjectSendStream[SessionMessage]
write_stream_reader: MemoryObjectReceiveStream[SessionMessage]
read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
async def ws_reader():
try:
async with read_stream_writer:
async for msg in websocket.iter_text():
try:
client_message = types.JSONRPCMessage.model_validate_json(msg)
except ValidationError as exc:
await read_stream_writer.send(exc)
continue
session_message = SessionMessage(client_message)
await read_stream_writer.send(session_message)
except anyio.ClosedResourceError:
await websocket.close()
async def ws_writer():
try:
async with write_stream_reader:
async for session_message in write_stream_reader:
obj = session_message.message.model_dump_json(by_alias=True, exclude_none=True)
await websocket.send_text(obj)
except anyio.ClosedResourceError:
await websocket.close()
async with anyio.create_task_group() as tg:
tg.start_soon(ws_reader)
tg.start_soon(ws_writer)
yield (read_stream, write_stream)