calling UploadFile for large file got exception with message "You cannot modify the position of a FtpDataStream. This property is updated as data is read or written to the stream."

FTP OS: not sure, probably Unix, the server is provided by GoDaddy: https://en.wikipedia.org/wiki/GoDaddy

FTP Server: not sure

Computer OS: ? Windows 7

<write details about your bug report / feature request here> I try to upload a big file (about 1.5GB) by FtpClient.UploadFile, but it always throws exception with the message: “You cannot modify the position of a FtpDataStream. This property is updated as data is read or written to the stream.” Tried to use FileZilla to upload such large file and it worked fine.

Small files can be uploaded (tried with files that are less than 500KB) normally by FtpClient.UploadFile

Logs :

fluent_ftp_log_file.txt

<paste logs here but DO NOT delete the lines above and below this line>

[Trox085]

I too am encountering this issue while being connected to FileZilla Server, but the error is not limited to just that server. It doesn’t happen all the time, but I have tracked down the top-level reason.

FluentFTP/Client/FtpClient_HighLevelUpload.cs line 1003 shows

							upStream = OpenAppend(remotePath, UploadDataType, true);
							upStream.Position = offset;

OpenAppend (FluentFTP/Client/FtpClient_LowLevel.cs line 1526) in turn calls OpenDataStream (FluentFTP/Client/FtpClient_LowLevel.cs line 810) which in turn calls OpenPassiveDataStream (FluentFTP/Client/FtpClient_LowLevel.cs line 306) or OpenActiveDataStream (FluentFTP/Client/FtpClient_LowLevel.cs line 578). Both OpenPassiveDataStream and OpenActiveDataStream return FtpDataStream instances.

/FluentFTP/Stream/FtpDataStream.cs line 54 shows

public override long Position {
			get => m_position;
			set => throw new InvalidOperationException("You cannot modify the position of a FtpDataStream. This property is updated as data is read or written to the stream.");
		}

This error occurs only when a socket error of 10054 occurring during a resumed upload. (FluentFTP/Client/FtpClient_HighLevelUpload.cs line 994).

[CHMaagaard]

I have encountered the same problem using a FileZilla server.