Android Question Issue with using FTPS on FTP library

amykonio said:

Hi.
I would first try to set passivemode to true.
Also, why are you using UseSSLExplicit = true? You should only use one of UseSSL = true and UseSSLExplicit = true. The first is more secure.
Take a look at the following link: What is FTP?

Andreas.

Click to expand...

1. Confirm Permissions on the NAS​

2. Passive Mode vs. Active Mode​

3. Adjusting the SSL Settings​

4. Detailed Error Logging​

5. Check Server Response Codes​

6. Test with Different FTP Client​

7. Review NAS FTPS Settings​

Revised Code Snippet​

Sub TestFTP(url As String, username As String, pwd As String, LocalPath As String)
    FTP.Initialize("FTP", url, 21, username, pwd)
    FTP.UseSSL = True
    FTP.UseSSLExplicit = True
    FTP.PassiveMode = True  ' Switch to Passive Mode

    Dim CustomSSL As CustomTrustManager
    CustomSSL.InitializeAcceptAll
    FTP.SetCustomSSLTrustManager(CustomSSL)

    FTP.List(LocalPath)
End Sub

JohnC said:

ChatGPT says...

From your description, it appears that the issues you're experiencing with your FTPS connection in your B4A (Basic4android) app are related to file permissions and possibly FTP command handling under FTPS mode. Here are a few suggestions and checks you might consider to resolve the issues:

1. Confirm Permissions on the NAS​

Ensure that the folder where you're trying to upload files has the correct write permissions for the user account used by the FTP connection. FTPS might be enforcing security measures more strictly compared to non-secure FTP, which might be why the issue appears only under FTPS.

2. Passive Mode vs. Active Mode​

You're currently using Active Mode (FTP.PassiveMode = False). FTPS often works better in Passive Mode due to how it handles data connections through firewalls and NATs. Try switching to Passive Mode by setting FTP.PassiveMode = True to see if this resolves the issue.

3. Adjusting the SSL Settings​

You have both FTP.UseSSL = True and FTP.UseSSLExplicit = True. Ensure that your NAS is configured to support explicit SSL (FTPS) on the port you are connecting to (commonly port 21 for explicit SSL). Some servers might require implicit SSL, which typically uses port 990.

4. Detailed Error Logging​

You're logging errors but consider adding more detailed logging around each step of your connection and upload process to help identify at which point the failure occurs. Also, ensure that LastException is being captured properly in all relevant places to get more detailed error messages.

5. Check Server Response Codes​

You mentioned getting "200 PORT command successful". This is generally a positive response in Active Mode indicating that the server successfully opened a port for a data connection. If switching to Passive Mode doesn't help, you may need to verify how your server handles data connections under FTPS.

6. Test with Different FTP Client​

Try using a desktop FTP client configured for FTPS with the same server settings and credentials. This can help determine if the issue is with the server configuration or the way your app is handling the FTPS connection.

7. Review NAS FTPS Settings​

Check the FTPS settings on your NAS. Make sure it's configured correctly to handle FTPS connections. Look for any specific settings related to data transfer modes or SSL/TLS requirements.

Revised Code Snippet​

Here’s a slightly adjusted version of your initial setup for testing with Passive Mode:

B4X:

Sub TestFTP(url As String, username As String, pwd As String, LocalPath As String)
    FTP.Initialize("FTP", url, 21, username, pwd)
    FTP.UseSSL = True
    FTP.UseSSLExplicit = True
    FTP.PassiveMode = True  ' Switch to Passive Mode

    Dim CustomSSL As CustomTrustManager
    CustomSSL.InitializeAcceptAll
    FTP.SetCustomSSLTrustManager(CustomSSL)

    FTP.List(LocalPath)
End Sub

Implement these suggestions one at a time to pinpoint which change effectively resolves the issue. If none of these help, you might need to dig deeper into the FTP server logs on your NAS or even consider contacting the NAS vendor for more detailed support regarding FTPS configurations.

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teddybear said:

1.Use ftp tools to check whether your Nas supports ftps first.
2.Please use code tags </> when posting code.

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