Mobile Apps - FTP allows 47 files transfer but after that fails completely

Asked By @maram

12-Nov-09 10:18 AM

Hi all,

I have an FTP client developed in .NET 2.0 (SP1) C# app. Files are
transferred correctly for the first 47 times. After that, it just
fails and that is it. I am using the passive mode. The range of ports
for PASV mode on the FTP server is 1050 to 3500. And all ports are
open on the server machine. Firewall is also alrite. I am saying all
this because when the FTP transfer starts to fail, I shutdown and
restart the emulator (windows mobile 6.0) and the transfer again
succeeds before failing at around 50 times.

After debugging, I found that I can login at the FTP server and issue
the PASV command and get the port at which I need to connect to the
FTP server to transfer files. But when I am trying to open the data
connection, it fails saying the "server has actively refused
connection". We can think that the emulator cannot connect to the FTP
server on that port, but then why does the transfer work OK when the
emulator is restarted?

I have searched a lot on this topic but without vain.
FYI: I am transferring the files NON-STOP (one after the other) in a
Thread in my .NET app.

Thanking you all for your time,

Best regards,
-A

16-Nov-09 05:16 PM

Which FTP implementation are you using?  Can you post some code in the loop
used to send the files?  It sounds like there is a memory/resource leak in
the FTP implementation or in your code.

17-Nov-09 11:16 AM

Hi Trevor,

Thanks for your response.

You've got a point. However, the FTP client (on the help) uses two
sockets: one to send FTP commands and the second one is for data
connection (sending or receiving files). How do we explain the fact
that I am able to login at the FTP server and send the PASV command, I
get the result and back and I calculate the port on which to connect
to the FRP server. When I perform the connect on the data connection
socket, then it does not work.

I am using Google group on the web. How do I upload my codes?

Thanks in advance,

Best regards,
-A

loop
in

17-Nov-09 03:01 PM

You can just copy/paste the code or use a Usenet client (Outlook
Express/Windows Live Mail) and connect to
microsoft.public.pocketpc.developer using the Microsoft mail server and
attach the file.  Are you writing your own FTP client from scratch?  There
are some .NET FTP clients from OpenNETCF and the native WinInet FTP API can
be called from C# using PInvoke (see FtpOpen, FtpPutFile, etc. on MSDN).  I
believe the OpenNETCF implementation is just a wrapper around WinInet to
make it work the same as the desktop .NET API.

19-Nov-09 11:45 AM

Does FtpClient have a FtpClient.Dispose method?  If so, that should be
called to free the resources used by the FtpClient.  I would recommend
creating a single FtpClient object outside of your loop and passing it into
your uploadFileToServer function so it can be re-used.  Try something like
this:

/********************************************/
This is my UploadThread
private void UploadFiles()
{
String uploadFileNameToMove = null;
String[] filesForUpload = null;

while (isUploadOn)
{
filesForUpload = Directory.GetFiles (UPLOAD_DIR);

if (filesForUpload == null || filesForUpload.Length == 0)