Hi.

I'm currently working with an application developed using libcurl in WinXP
and only one vsFTPd server.

The application shows an odd behavior, because in some machines, the
application works perfectly, connect to the vsftpd server using certificates
and it's able to upload a file without care about what IP address the client
uses (local or public), but in some other machines it's impossible to upload
files (using exactly the same application) without care of ip used. In a
third group of machines we are able to upload files only if the stations
uses local ip's (192.168.x.x) and we are unable to upload files if a public
address is used (190.x.x.x).

To discard a bad compilation or trouble with our application we tried to
upload files manually using other application (the
curl-7.19.6-devel-mingw32). We tried with this software in the same machines
and the results were the exactly the same.

Any client application (curl-7.19 and ours) correctly established the
control connection, the ftps server open the passive port and the client is
able to connect. Both TCP sockets shows as established in both extremes, but
the client don't send any data through the data connection.

We are using passive ftps. We configured vsftpd v2.1.2. The pki is self made
and is working correctly.

I know that is pretty odd that an IP address change in any way the behavior
of one application, but sadly is the result of our tests, and this
contribute to our confusion.

Obviously we have a software issue in some of our machines. Or some software
is needed in the clients or there is a conflict with some software.

My question is, someone have any information about any software that
conflict with libcurl? We disabled antivirus, firewalls, and any security
software.

We double checked that is not a network trouble, because we put sniffers on
the clients and the server and we can check that the client are not sending
any packets to the network. Magicly changing the IP some machines begin to
work.

Comparing the machines that transmits without trouble with the machines that
not transmit we can see that have different version of dll. Almost all the
machines that transmit uses winxp SP3. The only thing we can see it's that
we have many combinations of Internet Explorer. (IE7/SP3, IE6/SP3, IE6/SP2).
Our observations are something like:

IE7/SP3 works ok.
IE6/SP3 works local
IE6/SP2 don't work at all.

This can affect so much the behavior of a FTPs client?

We will upgrade some machines to check is something improves, but any hint
will be well received.

Attached traces from machine that don't work (failing), and machine that
only work local (working ok).

Thanks

Salvador