websocket.py•2.23 kB
import logging
from contextlib import asynccontextmanager
import anyio
from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
from starlette.types import Receive, Scope, Send
from starlette.websockets import WebSocket
import mcp.types as types
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[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 ws_reader():
try:
async with read_stream_writer:
async for message in websocket.iter_json():
try:
client_message = types.JSONRPCMessage.model_validate(message)
except Exception as exc:
await read_stream_writer.send(exc)
continue
await read_stream_writer.send(client_message)
except anyio.ClosedResourceError:
await websocket.close()
async def ws_writer():
try:
async with write_stream_reader:
async for message in write_stream_reader:
obj = message.model_dump(
by_alias=True, mode="json", exclude_none=True
)
await websocket.send_json(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)