diff --git a/cli/main.go b/cli/main.go
index 0c1e645..be622e6 100644
--- a/cli/main.go
+++ b/cli/main.go
@@ -225,52 +225,68 @@ func runHook(c *cli.Command) {
 	}
 }
 
-func keepAliveLoop(c *cli.Command, campusOnly bool) (ret error) {
-	logger.Infof("Accessing websites periodically to keep you online")
-
-	accessTarget := func(url string, ipv6 bool) (ret error) {
-		network := "tcp4"
-		if ipv6 {
-			network = "tcp6"
-		}
-		netClient := &http.Client{
-			Timeout: time.Second * 10,
-			Transport: &http.Transport{
-				DialContext: func(ctx context.Context, _network, addr string) (net.Conn, error) {
-					logger.Debugf("DialContext %s (%s)\n", addr, network)
-					myDial := &net.Dialer{
-						Timeout:       6 * time.Second,
-						KeepAlive:     0,
-						FallbackDelay: -1, // disable RFC 6555 Fast Fallback
-					}
-					return myDial.DialContext(ctx, network, addr)
-				},
+func newKeepAliveClient(network string) *http.Client {
+	dialer := &net.Dialer{
+		Timeout:       6 * time.Second,
+		KeepAlive:     0,
+		FallbackDelay: -1, // disable RFC 6555 Fast Fallback
+	}
+	return &http.Client{
+		Timeout: 10 * time.Second,
+		Transport: &http.Transport{
+			DialContext: func(ctx context.Context, _ string, addr string) (net.Conn, error) {
+				logger.Debugf("DialContext %s (%s)\n", addr, network)
+				return dialer.DialContext(ctx, network, addr)
 			},
-		}
-		resp, ret := netClient.Head(url)
-		if ret != nil {
-			return
-		}
-		defer resp.Body.Close()
-		logger.Debugf("HTTP status code %d\n", resp.StatusCode)
-		return
+		},
 	}
-	targetInside := "https://www.tsinghua.edu.cn/"
-	targetOutside := "https://www.baidu.com/"
+}
+
+func accessKeepAliveTarget(client *http.Client, url string) error {
+	resp, err := client.Head(url)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	logger.Debugf("HTTP status code %d\n", resp.StatusCode)
+	return nil
+}
 
-	stop := make(chan int, 1)
-	defer func() { stop <- 1 }()
+func startIPv6KeepAlive(stop <-chan struct{}, client *http.Client, url string, interval time.Duration) <-chan struct{} {
+	done := make(chan struct{})
 	go func() {
-		// Keep IPv6 online, ignore any errors
+		defer close(done)
+		timer := time.NewTimer(interval)
+		defer timer.Stop()
 		for {
 			select {
 			case <-stop:
-				break
-			case <-time.After(13 * time.Minute):
-				_ = accessTarget(targetInside, true)
+				return
+			case <-timer.C:
+				// Keep IPv6 online, ignore any errors.
+				_ = accessKeepAliveTarget(client, url)
+				timer.Reset(interval)
 			}
 		}
 	}()
+	return done
+}
+
+func keepAliveLoop(c *cli.Command, campusOnly bool) (ret error) {
+	logger.Infof("Accessing websites periodically to keep you online")
+	client4 := newKeepAliveClient("tcp4")
+	client6 := newKeepAliveClient("tcp6")
+	targetInside := "https://www.tsinghua.edu.cn/"
+	targetOutside := "https://www.baidu.com/"
+
+	stop := make(chan struct{})
+	done := startIPv6KeepAlive(stop, client6, targetInside, 13*time.Minute)
+	defer func() {
+		close(stop)
+		<-done
+		client4.CloseIdleConnections()
+		client6.CloseIdleConnections()
+	}()
 
 	errorCount := 0
 	for {
@@ -278,7 +294,11 @@ func keepAliveLoop(c *cli.Command, campusOnly bool) (ret error) {
 		if campusOnly || settings.V6 {
 			target = targetInside
 		}
-		if ret = accessTarget(target, settings.V6); ret != nil {
+		client := client4
+		if settings.V6 {
+			client = client6
+		}
+		if ret = accessKeepAliveTarget(client, target); ret != nil {
 			errorCount++
 			if errorCount >= settings.OnRetry {
 				ret = fmt.Errorf("keepAlive request error (re-login might be required): %w\n", ret)