superflexible

I solved it, apparently I was connecting with an FTP server in one thread and then uploading files in another.

I am now making sure that everything occurs in the same thread.

Hi,
I think I chose the thread subject wrong. 

My real question is if there are/were any issues with crashes in OpenSSL and how I can prevent them.

I don't want to discuss the pros and cons of threads.

Many thanks! I'll try it. And I'll look at the source code of TIcsFtpMultiThread to learn how it does the threading.

Hi,

many thanks for your reply! My application already creates the threads, there is no way around it. I cannot use a component that creates its own threads. The threads are already there.

I will look into it further and check if the latest ICS update maybe fixes the crashes.

Hello,

I am using TSslFtpClient in a multithreaded application. I get crashes inside the OpenSSL DLLs while uploading or downloading many smaller files in three separate threads (so three at a time).

I set the Multithreaded property to true.

I create all components in code, not in a DFM. So my question is, should I call TSslFtpClient.Create(nil) in the application's main thread, or in the thread where I am actually using it?

Currently I have a method CreateComponents which I call via TThread.Synchronize(nil,CreateComponents).

Are there any other precautions I have to take?

I read about all the async recommendations but I cannot redesign the application from scratch.

Many thanks.

Hello,

I don't think it will be easy ... personally I rewrote such code to use only a single wake-up event.

But a Google search for WaitForMultipleObjects linux does have some interesting results, for example:

https://news.ycombinator.com/item?id=20580626

There are Stackoverflow results too, but the site is down right now, so I can't check them.

Hi,

many thanks for double-checking on this, I will look into it and compare the two libraries. I didn't intentionally choose TLS 1.3 with Indy, but maybe it was chosen by the library.

And another customer did have problems with Indy too. So there might be other factors and it might still be a FileZilla bug.

Hi,

yes I agree it really looks like a FileZilla bug!

Many thanks for your help, I saw TLS 1.3 in your log and then I thought that might be it.

Hello,

I just tried it. Changes to GetSession or NewSession don't help because these functions are always called with the main FTP port, not the passive mode port number.

I just found that it works fine with TLS 1.3 but not with TLS 1.2! If you change it to 1.2, you can probably see the problem with your local FileZilla too.

Interesting. I guess not a problem then, I will just use TLS 1.3.

Hello,

many thanks, I will try this! I will also provide a server login to test for you, so you can see it happening for yourself.

Hello,

I have tested it with OverbyteIcsXferTst and I get the same error message. I am attaching two log files, a short one and a detailed one.

This is a very basic test installation of FileZilla Server v1.1.0. If necessary, I can provide an FTP test account.

filezillalog_short.txt

filezillalog_detailed.txt

Hello,

many thanks, I will try to set up a basic testing project and get log files next week.

So far only Indy works with FileZilla server, for me. It would be good to have an alternative.

Hello,

I am using TSslFtpClient.

I will try TIcsFtpMulti.

As you know, the FTP protocol makes two connections, a control channel and a data channel. FileZilla FTP Server requires that these two connections share the same TLS session (or session ID).

If the data channel tries to open an independent TLS session, the server rejects it for security purposes.

The Internet is full of problem reports related to "TLS session of data connection has not resumed". In older FileZilla Server versions, the requirement could be turned off, but now it is mandatory.

Hello,

I am using ICS v8.67.

Trying to make an FTP connection to a FileZilla FTP server, I get:

425 Unable to build data connection: TLS session of data connection not resumed.

Is there a setting to share the TLS session between the control and data channels?