Hi,
as I see the H2Connection.outbound_flow_control_window is not updated in the initial SETTINGS exchange.
I put these lines after event handling loop:

           events = self.conn.receive_data(data)
            for event in events:
                if isinstance(event, ResponseReceived):
                    self.handle_response_received(event)
                elif isinstance(event, DataReceived):
                    self.handle_data_received(event)

:
:
data = self.conn.data_to_send()
if data:
self.writer.write(data)

            **print('self.conn.outbound_flow_control_window:', self.conn.outbound_flow_control_window)
            print('self.conn.remote_settings.initial_window_size:', self.conn.remote_settings.initial_window_size)**

and I see that self.conn.outbound_flow_control_window is not updated according to the initial SETTINGS frame but self.conn.remote_settings.initial_window_size is correct.

The result is that even the remote side can handle more data so does not send any WINDOW_UPDATE but the local peer will not send any data because it thinks that remote side is full