async def connection_down(self, interface: Interface):
        '''A connection to server either went down, or was never made.
        We distinguish by whether it is in self.interfaces.'''
        if not interface: return
        if interface.server == self.default_server:
            self._set_status(ConnectionState.DISCONNECTED)
        await self._close_interface(interface)
        util.trigger_callback('network_updated')
A connection to server either went down, or was never made.
        We distinguish by whether it is in self.interfaces.
electrum/network.py