PYTHON-5543 PyMongoBaseProtocol should inherit from asyncio.BaseProtocol (#2528)

Co-authored-by: Noah Stapp <[email protected]>

Author: aclark4life

doc/changelog.rst

@@ -10,6 +10,9 @@ Version 4.15.1 is a bug fix release.
    that would cause a ``TypeError`` when using ``pymongocrypt<1.16`` by passing an unsupported ``type_opts`` parameter even if
    Queryable Encryption text queries beta was not used.
 
+- Fixed a bug in ``AsyncMongoClient`` that caused a
+  ``ServerSelectionTimeoutError`` when used with ``uvicorn``, ``FastAPI``, or ``uvloop``.
+
 Issues Resolved
 ...............
 
@@ -18,7 +21,6 @@ in this release.
 
 .. _PyMongo 4.15.1 release notes in JIRA: https://jira.mongodb.org/secure/ReleaseNote.jspa?projectId=10004&version=46486
 
-
 Changes in Version 4.15.0 (2025/09/10)
 --------------------------------------
 

pymongo/network_layer.py

@@ -22,7 +22,7 @@
 import struct
 import sys
 import time
-from asyncio import BaseTransport, BufferedProtocol, Future, Protocol, Transport
+from asyncio import BaseProtocol, BaseTransport, BufferedProtocol, Future, Transport
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -250,7 +250,7 @@ def recv_into(self, buffer: bytes | memoryview) -> int:
         return self.conn.recv_into(buffer)
 
 
-class PyMongoBaseProtocol(Protocol):
+class PyMongoBaseProtocol(BaseProtocol):
     def __init__(self, timeout: Optional[float] = None):
         self.transport: Transport = None  # type: ignore[assignment]
         self._timeout = timeout