Initial import

mcp_python/server/stdio.py

@@ -0,0 +1,60 @@
+import sys
+from contextlib import asynccontextmanager
+
+import anyio
+import anyio.lowlevel
+from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
+
+from mcp_python.types import JSONRPCMessage
+
+
+@asynccontextmanager
+async def stdio_server(
+    stdin: anyio.AsyncFile | None = None, stdout: anyio.AsyncFile | 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[JSONRPCMessage | Exception]
+    read_stream_writer: MemoryObjectSendStream[JSONRPCMessage | Exception]
+
+    write_stream: MemoryObjectSendStream[JSONRPCMessage]
+    write_stream_reader: MemoryObjectReceiveStream[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 = 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)
+                    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