func (api *Api) Addr() net.Addr {
	if api.listener == nil {
		return nil
	}
	return api.listener.Addr()
}
func (api *Api) Addr() net.Addr {
	if api.listener == nil {
		return nil
	}
	return api.listener.Addr()
}
// Addr returns binded socket address. For bind port 0 in tests