Transfer of files with '->' in their names fails with 'unexpected end of stream' error

[patrr]

I noticed this error trying to transfer from my Linux PC to my Android smartphone a file named '1a_Orléans->Meung-sur-Loire (19km).gpx', which is a legit filename under Linux.
I don't know if this behaviour is intended or not, but anyway the error message 'unexpected end of stream' is somewhat misleading and the user could never suspect to be hitting against a (undocumented?) constraint on filenames.
Pixel 7a; Android 16; FTP Server 3.1 - 30100 (16-36)
Thanks

[Xavron]

Re-edited as looked into it further to find something that could show it, and clear things up.

Couldn't find anything in Android source code to show it. Android has some oddities that nothing can be done except to workaround.

• A potential issue to fix here in Swiftp is to return a better error. Its very subjective what should be done about it, even if anything. This is the only reason I see to keep this open.

I have a note around here somewhere about looks like it was "?" being denied. There's nothing I could do about that one as its Android/filesystem itself.

• Discussion from another project as a simple showing to why Swiftp cannot do this (as in its not me at fault in my own post here :-) https://github.com/syncthing/syncthing/issues/9395 Title: Add error message when filename contains illegal characters for target storage, Partial quote: "On Linux, ? and : are valid characters for filenames. On Android, they are not." (Disabled link so this doesn't show up in their project so just copy paste instead.)

• There is a very incredibly hacky workaround that could be done. Would only be able to correctly access files via FTP though. But, could store a DB of adjusted name > original name. When FTP has a request for original name, rename to original and send bytes or add to list. Many or all people might never attempt this. It comes with major confusion unless the files are stored where the user cannot access them without FTP. Certainly could be put behind a setting. Just adding this as it is a possibility even if no one would ever do it.

• You can confirm directly on Android using a file manager. A test using Samsung Files in Android 15 denies use of ">" and "<" and "/", "*", and more in file names.

Alternatives to dealing with it:

• Auto batch rename

• Block the files

• Containerize then use naming on the container where it passes Android use eg Deja Dup, gzip tar, restic, etc.

• Android's upcoming built-in Linux might do better if it can support it in some way - I suppose this is going to be unlikely but it could also be possible. Although, Swiftp wouldn't work there but could in theory use anything else for FTP server. Should expect this as unlikely for some years, if ever. Only time will tell.

  • I have it available on one device, but it has the appearance that the device's chipset doesn't support it: https://android.googlesource.com/platform/packages/modules/Virtualization/+/refs/tags/android-16.0.0_r1/libs/framework-virtualization/src/android/system/virtualmachine/VirtualMachineConfig.java#1220