def addReader(self, reader):
        """
        Add a socket FileDescriptor for notification of data available to read.
        """
        if reader not in self._reads:
            self._reads[reader] = self._makeSocketEvent(
                reader, 'doRead', FD_READ | FD_ACCEPT | FD_CONNECT | FD_CLOSE)
            # If the reader is closed, move it over to the dictionary of reading
            # descriptors.
            if reader in self._closedAndNotReading:
                self._closedAndReading[reader] = True
                del self._closedAndNotReading[reader]

        Add a socket FileDescriptor for notification of data available to read.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/win32eventreactor.py