// note that unlike tcp connections, reading is a good enough test here.
			_, err := conn.readMessage(time.Second / 100)
			switch {
			case !errors.Is(err, os.ErrDeadlineExceeded):
				log.Debugf("ztunnel keepalive failed: %v", err)
				if errors.Is(err, io.EOF) {
					log.Debug("ztunnel EOF")
					return nil
				}
				return err
			case err == nil:
				log.Warn("ztunnel protocol error, unexpected message")