add optional sid argument to disconnect function

flask_socketio/__init__.py

@@ -833,7 +833,7 @@ def rooms(sid=None, namespace=None):
     return socketio.server.rooms(sid, namespace=namespace)
 
 
-def disconnect(silent=False):
+def disconnect(sid=None, silent=False):
     """Disconnect the client.
 
     This function terminates the connection with the client. As a result of
@@ -845,8 +845,10 @@ def receive_message(msg):
                 disconnect()
             # ...
 
+    :param sid: The session id of the client. If not provided, the client is
+                obtained from the request context.
     :param silent: this option is deprecated.
     """
     socketio = flask.current_app.extensions['socketio']
-    return socketio.server.disconnect(flask.request.sid,
+    return socketio.server.disconnect(sid or flask.request.sid,
                                       namespace=flask.request.namespace)