FluentFTP | FTPS client for .NET & .NET Standard | FTP library

To read file to a string using FluentFTP, you can use FtpClient.Download method that either writes the file contents to Stream or byte[] array. The following examples uses the latter.

Probably both are like this: img00012.jpg -> myPicture_001_summer.jpg.jpg, because you have checked the "Hide extensions for known files" in one of the computers.

So, open a Windows Explorer > See/View > Options > See/View > Hide Extensions for known files (could be a little different, my language is not EN).

You can see my test file in C:\home\site\wwwroot\aa.bak. And use code like you, it works fine.

So I recommand you, try my code, and check the result. If the problem is solved, then it is really great.

If not, I dare to conclude that there is a problem with your file reading. And you need check below code. Or show more details for us.

Download the file directly to the HTTP output stream with use of FtpClient.Download and HttpResponse.OutputStream:

Use:

• ConcurrentBag class to implement a connection pool;
• Parallel class to parallelize the operation;
• ParallelOptions.MaxDegreeOfParallelism to limit number of the concurrent threads.

.NET framework does not support TLS/SSL session reuse. If your server requires it (what it looks it does), you cannot use FtpWebRequest nor FluentFTP. Both use the .NET implementation of TLS/SSL.

You will have to use FTP library that uses own TLS/SSL implementation.

You can use my WinSCP .NET assembly. Though contrary to FluentFTP, it's not a native .NET library, it has dependencies on an external binary. But that's what makes it working.

Some references:

• https://github.com/robinrodricks/FluentFTP/issues/347
• https://github.com/dotnet/runtime/issues/27916
• "Authentication failed because the remote party has closed the transport stream" when transferring to/from FTP server over TLS/SSL using FluentFTP
• Upload file to implicit FTPS server in C# with TLS session reuse
• Suddenly getting "150 Opening Data channel for file download from server" after the FTP downloads was working for years – According to this post and other references elsewhere, the TLS/SSL session reuse was supported earlier with .NET Framework, but some update broke it. In .NET Core it was never working (see also the dotnet GitHub link above).

I think, you have a deadlock in line:

It seems that you are using one FtpClient instance for all your transfers.

The FtpClient represents one connection to an FTP server. FTP protocol does not allow multiple parallel transfers over one connection. You have to open a new connection for every parallel transfer.

First of all, you don't create directly a CancellationToken, you create a CancellationTokenSource and get it's Token.

Said that, you can imagine the use of that token, to allow to cancel the operation. You can do something like this: