Close TCP connection

        :returns: close status (True for close/None if already close)
        :rtype: bool or None

def close(self):
        """Close TCP connection

        :returns: close status (True for close/None if already close)
        :rtype: bool or None
        """
        if self.__sock:
            self.__sock.close()
            self.__sock = None
            return True
        else:
            return None