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https://issues.apache.org/jira/browse/NET-686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17221401#comment-17221401
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JRRR commented on NET-686:
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Thanks for the prompt replies!
@[~ggregory]
Sorry, what do you mean exactly?
@[~b.eckenfels]
It might be a problem with maybe Android itself (the non-Apache socket code
works fine in a normal Windows app) but the library doesn't do anything to work
around it and the whole time I've been working on my app (probably more than a
year by now) I haven't found a way around it either.
The bug happens with both Android Studio's emulator and a real phone or tablet.
All the devices are only "online" within the same network: The Emulator through
the LAN connection of the PC, the phone via wifi but they don't actually need
internet access, as both servers (1x Linux, 1x Windows) are within the same
network too (I access them via "10.1.1.xxx"). I haven't found a proper public
server that I can thoroughly test this with because the existing ones delete
uploaded files either instantly or every 30 minutes.
> Most files aren't downloaded completely from an FTP server
> ----------------------------------------------------------
>
> Key: NET-686
> URL: https://issues.apache.org/jira/browse/NET-686
> Project: Commons Net
> Issue Type: Bug
> Components: FTP
> Affects Versions: 3.6, 3.7.2
> Environment: Win 10
> Java 8
> Android Studio 3.6.1 (min SDK 24, target SDK 27)
> Reporter: JRRR
> Priority: Major
> Attachments: 2a-original.png, 2b-corrupt.png, 2c-corrupt.png,
> 5a-original.jpg, 5b-corrupt.jpg, 5c-corrupt.jpg, DownloadProblem.java
>
>
> About a month ago I opened another
> [issue|https://issues.apache.org/jira/browse/NET-684] that was closed because
> it wasn't reproducible with macOS and a public FTP server.
> Short summary: Downloading files from an FTP server results in these files
> randomly missing bytes. It looks like the download always "completes" and
> there are no error messages/exceptions but random bytes in random files are
> simply skipped. Images (jpg & png) are usually affected more (up to 30, maybe
> 40, bytes smaller than the original), and are then also visibly corrupt, than
> text files (usually only 2-3 bytes smaller, rarely more).
> I'm working on an Android app (Win 10, Java 8, Android Studio 3.6.1, min SDK
> 24, target SDK 27), which I'm testing with FTP servers in the same network
> (1x Win 10, 1x Linux, both accessed via IP - "10.1.1.xxx"). No matter what
> method in the library I use (retrieveFile, retrieveFileStream,
> sendCommand(FTPCmd.RETRIEVE, filename)), most of the time there's at least a
> single file that's corrupted.
> I also tested the same code with public servers and even though I didn't have
> a lot of time because those servers regularely delete uploaded files, I never
> experienced said problem with them.
> I even wrote my own mini-library (just for login/logout and download) using
> Java's default "Socket" but I still had the same problem on Android Studio's
> simulator/a real device. BUT: When I used the same code to create a small
> Windows/Swing/Java app, there were no more corrupted files.
> It looks like this bug is only affecting a very specific combination of
> OS,...:
> Android (emulator/real device) + Java (8) + FTP server in the same network
> (accessed via IP)
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