https://bugs.kde.org/show_bug.cgi?id=522451
Bug ID: 522451
Summary: KDE Connect file transfers fail or become very slow
with ASUS RT-AX88U Pro IGMP Snooping enabled
Classification: Applications
Product: kdeconnect
Version First 26.04.2
Reported In:
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: desktop-application
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
DESCRIPTION
KDE Connect file transfers between Android and Fedora were very slow or failed
intermittently when using my home Wi-Fi through an ASUS RT-AX88U router with
IGMP Snooping enabled.
Pairing and basic device discovery worked, but file transfers often stalled,
became extremely slow, or needed several attempts. Fedora's firewall was not
the issue: the active firewalld zone allowed the `kdeconnect` service.
The issue disappeared completely when IGMP Snooping was disabled on the ASUS
router. Transfers also worked perfectly when Fedora was connected to the Pixel
phone's hotspot instead of the home router.
I am not sure this is a KDE Connect bug, since the router appears to be
mishandling multicast/mDNS traffic. However, it may be useful as a
troubleshooting/documentation case, or possibly as a diagnostics issue: KDE
Connect did not show a clear user-facing indication that multicast/mDNS or the
local link was unstable.
STEPS TO REPRODUCE
1. Use KDE Connect between an Android phone and a Fedora KDE desktop on the
same 5 GHz Wi-Fi network.
2. Use an ASUS RT-AX88U Pro router with IGMP Snooping enabled.
3. Pair the devices successfully.
4. Try sending files between the phone and the Fedora desktop.
5. Disable IGMP Snooping on the router and try the same transfers again.
OBSERVED RESULT
With IGMP Snooping enabled, file transfers are very slow, intermittently fail,
or require multiple attempts. Device pairing and basic connection may still
appear to work.
In the Android KDE Connect log, during a transfer, I saw entries such as:
* Beginning to send payload for kdeconnect.share.request
* MdnsDiscovery: Service lost
* Finished sending payload
* BackgroundJobHandler: afterExecute got a CancellationException
* Later, the devices reconnected and completed a TLS handshake again
With IGMP Snooping disabled, KDE Connect file transfers work normally and
reliably.
EXPECTED RESULT
KDE Connect file transfers should either work reliably on a normal local Wi-Fi
network, or provide clearer diagnostics/user-facing feedback when the local
network/mDNS/multicast path is unstable.
It may also be useful to document IGMP Snooping/multicast handling on some
consumer routers, especially ASUS routers, as a possible workaround for
intermittent discovery or file transfer problems.
SOFTWARE/OS VERSIONS
Android device:
Google Pixel 10
Android 16
KDE Connect Android: 1.35.9
Desktop:
Fedora KDE
KDE Connect desktop: 26.04.2
Operating System: Fedora Linux 44
KDE Plasma Version: 6.7.0
KDE Frameworks Version: 6.27.0
Qt Version: 6.11.1
Network/router:
ASUS RT-AX88U Pro
Wi-Fi: 5 GHz only
Guest network: not used
Band switching: not used
Workaround: disabling IGMP Snooping fixed the issue completely
ADDITIONAL INFORMATION
The issue does not occur when Fedora connects to the Pixel phone hotspot. This
suggests that KDE Connect itself, Fedora's firewall, and basic Android/Desktop
pairing are working correctly, and that the problem is related to the router's
multicast/mDNS/IGMP Snooping behavior.
Fedora firewalld active zone included the `kdeconnect` service.
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