asyncore.py: poll2() :
--------------------
if flags:
    # Only check for exceptions if object was either readable
    # or writable.
    flags |= select.POLLERR | select.POLLHUP | select.POLLNVAL
    pollster.register(fd, flags)
--------------------

This is unexpected behaviour. Why descriptor does not get polled if neither read nor write selected ? So I can not track dropping of connection if I do not want neither read nor write. I think "if flags:" should be removed.