So the sequence of events seems to be:
  asyncore.readwrite calls obj.handle_read_event
  ... which calls obj.handle_read (3rd branch of handle_read_event)
  ... which is defined in asynchat.py;  it calls obj.recv
  ... (back in asyncore now): recv calls obj.socket.recv
  ... and gets no data, so it then calls obj.handle_close
  ... which calls obj.close(), and so closes obj.socket as well.

and now obj.handle_expt_event gets confused because the socket is 
closed.

Now what?