Android Question FTPServer example not working with DirInternal

[thoward]

I downloaded the B4A FTP Server library and example from here: https://www.b4x.com/android/forum/t...mplemented-with-socket-and-asyncstreams.74320
When I ran it as-is, it worked exactly as expected. I can use WinSCP or Windows explorer on my PC to transfer files to/from my phone.

However, when I change the BaseDir to File.DirInternal, I cannot even connect with an FTP client anymore. I've gone back and forth several times to make sure I'm not imagining things.

Is there something I'm missing? You can use DirInternal for the FTP server, can't you?

Thanks in advance for any help!

Tim

 

[JohnC]

Are there any errors listed in the right-hand log list of the IDE?

 

[thoward]

Are there any errors listed in the right-hand log list of the IDE?

No, there are no errors, but there is some log information. I'll post that when I get a chance.

 

[edgar_ortiz]

Use File.DirDefaultExternal

You can check:

File.DirInternal & File.DirDefaultExternal

HI, I am using a SQLite database in my app. When I create it, where would be the best place to save it on the device ? I have read that the file can be saved in File.DirDefaultExternal and also read it can be put in File.DirInternal. I want to be able to keep this file after a app update or...

www.b4x.com

 

[thoward]

Use File.DirDefaultExternal

You can check:

File.DirInternal & File.DirDefaultExternal

HI, I am using a SQLite database in my app. When I create it, where would be the best place to save it on the device ? I have read that the file can be saved in File.DirDefaultExternal and also read it can be put in File.DirInternal. I want to be able to keep this file after a app update or...

www.b4x.com

Nope. My app's files are in DirInternal. That's where I need them to be. I also need the FTP Server to use DirInternal, so I can transfer the files to a PC.

 

[JohnC]

If for some reason FTP is not compatible with DirInternal, couldn't you use rp.GetSafeDirDefaultExternal("") and just manage your files in that directory (and copy them from DirInternal) as a worse case scenario?

 

[edgar_ortiz]

Nope. My app's files are in DirInternal. That's where I need them to be. I also need the FTP Server to use DirInternal, so I can transfer the files to a PC.

Ok

 

[thoward]

If for some reason FTP is not compatible with DirInternal, couldn't you use rp.GetSafeDirDefaultExternal("") and just manage your files in that directory (and copy them from DirInternal) as a worse case scenario?

For security reasons, I have to avoid placing the files into any folder that is accessible by another app. Would GetSafeDirDefaultExternal provide that?

 

[Erel]

Use File.DirDefaultExternal

Never use File.DirDefaultExternal. It is always a mistake.
Use RuntimePermissions.GetSafeDirDefaultExternal instead.

I don't see any reason why it shouldn't work with File.DirInternal.

 

[thoward]

After rebooting both my phone and the PC, I can connect to the FTPServer example using DirInternal. However, I am unable to change directories or transfer files either direction from DirInternal.

Here is the log from connecting and changing directories using DirRootExternal, which is what is included in the sample. I was also able to transfer files just fine.

--------- beginning of main
Copying updated assets files (1)
*** Service (starter) Create ***
** Service (starter) Start **
** Activity (main) Create, isFirst = true **
** Activity (main) Resume **
** Activity (main) Pause, UserClosed = false **
sending message to waiting queue (activity_permissionresult)
running waiting messages (1)
** Activity (main) Resume **
client: USER Test
client: PASS test
User logged in: Test
client: SYST
client: FEAT
client: OPTS UTF8 ON
client: PWD
client: CWD /DCIM/Camera
CurrentPath: /DCIM/Camera
client: PWD
client: TYPE A
client: PASV
client: LIST -a
Data connection terminated: /DCIM/Camera
DataConnection_Close
client: CWD /DCIM
CurrentPath: /DCIM
client: PWD
client: TYPE A
client: PASV
DataConnection_Close
client: LIST -a
Data connection terminated: /DCIM
DataConnection_Close
client: CWD /
CurrentPath: /
client: PWD
client: TYPE A
client: PASV
DataConnection_Close
client: LIST -a
Data connection terminated: /
DataConnection_Close
client: PWD
client: PWD
client: TYPE A
terminated
DataConnection_Close

After changing to DirInternal, I get this:

*** Service (starter) Create ***
** Service (starter) Start **
** Activity (main) Create, isFirst = true **
** Activity (main) Resume **
client: USER Test
client: PASS test
User logged in: Test
client: SYST
client: FEAT
client: OPTS UTF8 ON
client: PWD
client: CWD /
Data connection terminated: /
DataConnection_Close
Data connection terminated: /
DataConnection_Close
client: TYPE I
client: PASV
DataConnection_Close
client: RETR app_allow_list.txt
Data connection terminated: null
DataConnection_Close
client: CWD virtual_assets
terminated
DataConnection_Close

On the FTP client side (WinSCP), I get this error:
Copying files from remote side failed.
Invalid path: app_allow_list.txt

Or transferring from the PC to the phone, I get this:
Copying files to remote side failed.
Invalid path: image1.jpg

 

[thoward]

I have unpacked the FTPServer.b4xlib file and changed the example project to use the .bas files instead of the library. Now I'm trying to troubleshoot and see where it's going off the rails.

 

[JohnC]

In the top set of events you posted (where you are not using DirInternal), it seems like you are just navigating to directories and doing a list command.

But, then in the later events (when you are having problems) it seems that you are trying to work with files and not directories, so maybe the cause of your problem is a syntax issue of not having the path and/or filename specified correctly.

 

[thoward]

Okay, I think I may have something. In FTPClient.NormalizePath, it assumes that the results of the Java method "getCanonicalPath" are going to be the same as BaseDir, which is what we set to DirInternal. This is a correct assumption for DirRootExternal, but (at least on my phone) appears to be incorrect for DirInternal. Take a look at the code:

Private Sub NormalizePath(p As String) As String
    If p.StartsWith("/") Or p.StartsWith("\") Then p = p.SubString(1)
    
    '#if B4A Or B4J
    Dim jo As JavaObject
    jo.InitializeNewInstance("java.io.File", Array(File.Combine(mServer.BaseDir, p)))
    Dim CanonicalPath As String = jo.RunMethod("getCanonicalPath", Null)
    If CanonicalPath.ToLowerCase.StartsWith(mServer.BaseDir.ToLowerCase) Then
        Dim r As String = CanonicalPath.SubString(mServer.BaseDir.Length).Replace("\", "/")
        If r.Length = 0 Then Return "/" Else Return r
    Else
        SendResponse(450, "Invalid path: " & p)
        Return ""
    End If
    '...
End Sub

When I set BaseDir to DirRootExternal -
BaseDir: /storage/emulated/0
CanonicalPath: /storage/emulated/0

When I set BaseDir to DirInternal -
BaseDir is /data/user/0/b4a.example/files
CanonicalPath is /data/data/b4a.example/files

I believe this is why DirInternal is not working for me.

 

[thoward]

As a test, I changed line 7 above to this

Dim CanonicalPath As String = File.Combine(mServer.BaseDir, p)

Now, everything works for both DirInternal and DirRootExternal, as far as I can tell.

I'm not sure why getCanonicalPath was used to begin with, but I'm sure @Erel had a good reason for it.

 

[Erel]

I'm not sure why getCanonicalPath was used to begin with, but I'm sure @Erel had a good reason for it.

It is a safety procedure to prevent the client from trying to access folders outside of the base folder.
It is less relevant if the base folder is the internal folder, assuming that you are fine with the customer accessing all of the files there.