Could you please give me an assistance on how to understand the mechanism of WinSCP????

Hi Martin,

I'm from Viet Nam Telecommunications Authority. I'm in charge of managing Quality of service in telecommunication field.

I highly appreciate your tool on testing Internet speed.

I have already given your tool a trial and wondering that tested speed are always close to advertised speed of service provider. Futhermore, your tested speed always much higher than that which I tested through my own tools or other tools provided by other webistes.

It will be highly appreacity if you are pleased to give me the mechanisms and methodology of your tools. This will definitely assist us in exploring advance tools in managing Internet service in Viet Nam.

Thank you in advance for your support

Best reagards
Thinh Vu Trong
Viet Nam Telecommunications Authority

While Martin is a very good developer, I don't believe he is a magician or has somehow managed to circumvent the laws of physics :mrgreen:

As we can safely assume that WinSCP uses the standard internet protocols, the best place to start is to read about them, specifically SCP and SFTP:
https://en.wikipedia.org/wiki/Secure_copy_protocol
https://en.wikipedia.org/wiki/SSH_File_Transfer_Protocol

WinSCP is also open source and the code is freely available to read and understand:
https://sourceforge.net/projects/winscp/files/WinSCP/

Implementation details may vary but generally there is no black magic involved in file transfer protocols.

SCSI on the other hand...

"Getting a SCSI chain working is perfectly simple if you remember that there
must be exactly three terminations: one on one end of the cable, one on the
far end, and the goat, terminated over the SCSI chain with a silver-handled
knife whilst burning *black* candles."

What protocols are you using for testing? What are the other tools you have used?

Anyway, I have posted some answers on Server Fault about differences in SFTP clients performance (if that's the protocol your question is about).
They may give you some background:

https://serverfault.com/q/694062/168875#694063
https://serverfault.com/q/843691/168875#843722
https://serverfault.com/q/700780/168875

Thank you for your support

I am currently using FTP protocol in testing Internet speed (upload/download), we have two ways to test Internet speed now including
1. My own tool developed via the usage of "PowerTCP for ActiveX" library - Dart Communication.
2. We login to FTP server using File explorer in Window 7 OS in order to test Internet speed

We both get the same internet speed through 2 my own mentioned methods but much slower than your tool – WinSCP

I will highly appreciate if you kindly give me an clear explanation relating to above issues.

Once again, Thank you so much!

With FTP protocol, the improvement can be caused by large socket buffers that WinSCP uses.

Check SO_RCVBUF and SO_SNDBUF.
https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-setsockopt

Thank you for your response,

According to your suggestion link I have learned and found the cause is like that.
This makes me think if the old libraries did not set up large socket buffers like winscp.
I then tried to download the PowerTCP FTP for .NET example at Dart Communication, and tested it with the speed of WinSCP.
So the same developer, with two different libraries (PowerTCP FTP for ActiveX and PowerTCP FTP for .NET), gave different results.
Can you tell me how are you setting up socket buffers? Which value is optimal?

Thank you very much!

Hello Martin,
I have contacted Dart Communication and they also say like you "You may be able to improve your performance by adjusting the Ftp.ReceiveBufferSize and Ftp.SendBufferSize properties". Can WinSCP be adjustable like that?

vtthinh wrote:

Can you tell me how are you setting up socket buffers? Which value is optimal?

SO_RCVBUF is 4MB.
SO_SNDBUF is dynamic. Do research on SIO_IDEAL_SEND_BACKLOG_QUERY.

vtthinh wrote:

I have contacted Dart Communication and they also say like you "You may be able to improve your performance by adjusting the Ftp.ReceiveBufferSize and Ftp.SendBufferSize properties". Can WinSCP be adjustable like that?

Buffer sizes are not configurable in WinSCP.