Calibre content server - issues downloading .cbz and .cbr files over Wi-Fi

[Shiftedwrath]

Hopefully I am posting this in the right forum, if not feel free to move it.

I am using the built-in Calibre content server (running on a Windows Server 2019 VM) to access my books and comics. While it has worked flawlessly on a Windows 10 desktop over a wired connection, I am running into issues when trying to load comics (.cbr and .cbz formats) on Wi-Fi devices.

The issue is somewhat inconsistent, but most of them time when I try to open a comic, some of the .jpg files in the archive will fail to download with a "network error" message. The exact files that fail are random, it differs every time.

I have rebuilt the .cbz archive and verified the files inside. The comic downloads just fine over a wired connection. The issue is happening with larger files (like comics), but EPUB/AZW3 files work just fine.

My network consists of two Ubiquity UniFi UAP-AC-PRO access points.

The devices I am testing on are a Kindle Fire HD 10 (2019) and Samsung Galaxy Note 8. I'm using the Google Chrome (Android) web browser, but other browsers have the same issue.

I've tried rebooting all devices/equipment and clearing the browser cache. Other apps seem to work fine over Wi-Fi, the issue appears to be specific to Calibre.

Any assistance is appreciated. Thank you!

[DNSB]

Originally Posted by Shiftedwrath

Any assistance is appreciated. Thank you!

Are you NATting or bridging the VM's network connection?

[Shiftedwrath]

Originally Posted by DNSB

Are you NATting or bridging the VM's network connection?

Sorry I should have clarified, the VM is on the same network as the clients I'm trying to access from. Nothing special with the connection, it just has a single network adapter with a (local) static IP assigned.

[kovidgoyal]

The server itself has absolutely nothing in it that cares in any way about what the network transport is, it just writes to the TCP socket provided by the operating system. If you are getting transfer errors over only WiFi it points to network stability issues, at a level lower than the server. You can look at the server logs to see what error code if any is being reported by the OS.

[Shiftedwrath]

Originally Posted by kovidgoyal

The server itself has absolutely nothing in it that cares in any way about what the network transport is, it just writes to the TCP socket provided by the operating system. If you are getting transfer errors over only WiFi it points to network stability issues, at a level lower than the server. You can look at the server logs to see what error code if any is being reported by the OS.

Thanks for the response. I agree that it seems like a Wi-Fi issue, although the clients do not show packet loss or other errors.

I did check the Windows event logs on the server and there are no errors. The Calibre server log repeats two error messages: "An established connection was aborted by the software in your host machine" and "An existing connection was forcibly closed by the remote host". The error messages occur as it tries to send unpacked image files to the client.

I understand that Calibre is primarily an eBook software, and works great in that capacity - none of the clients have any issues downloading EPUB/MOBI/AZW3 files.

I'm hoping that someone has experienced a similar issue, perhaps even with UniFi networking equipment, and can share some insight. I will continue troubleshooting on my end.

[kovidgoyal]

Try rebooting into safe mode with networking, or try temporarily disabling antivirus/firewall, those are often the cause of unexplained network issues.

[Shiftedwrath]

Re-posting this as my previous reply was incomplete, and I am not allowed to edit. If anyone can delete the previous reply I'd appreciate it.

I did some more extensive testing while I was at work (my server is accessible outside my network).

Here are the results of each test:
1.) Windows 7 desktop - wired - Chrome web browser - no issues
2.) Windows 7 laptop - Wi-Fi - Chrome web bowser - no issues
3.) Galaxy Note 8 - Wi-Fi - Chrome (Android) web browser - comics fail to download
4.) Galaxy Note 8 - Wi-Fi - Edge (Android) web browser - comics fail to download
5.) Galaxy Note 8 - Wi-Fi - Firefox (Android) web browser - no issues
6.) Kindle Fire HD 10 (2019) - Chrome (Android) web browser - comics fail to download
7.) Kindle Fire HD 10 (2019) - Silk (Android) web browser - comics fail to download
8.) Kindle Fire HD 10 (2019) - Firefox (Android) web browser - no issues

So it seems the common factor is Chromium-based browsers on Android devices. I don't have any iOS devices so I'm unable to test other platforms.

Using Firefox is a 100% viable workaround, but I'm curious as to the cause, maybe there is a browser setting that can be adjusted? I will update this if I discover anything further.

For anyone wanted to reproduce:
1.) Add .cbz or .cbr files to your Calibre web server
2.) Try to download the files from an Android device using a Chromium-based web browser (Chrome, Edge, Silk)
3.) Most of the time the download will fail with a "network error" message. Larger file sizes will fail more frequently

[kovidgoyal]

How large are these comics, for curiosities sake?

[Shiftedwrath]

Originally Posted by kovidgoyal

How large are these comics, for curiosities sake?

Looks like my previous reply went through - sorry for the incomplete post. The comics I tested are between 30MB and 300MB in size. The issue seems to happen regardless of file size, but happens more frequently with larger sizes.

[kovidgoyal]

I tried downloading a 103MB file three times with chrome on android, no failures.

[ownedbycats]

Just a random thought: does your router use any sort of QoS? I wonder if somehow that might be throttling the images and killing the connection.