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I've created a simple SFTP upload tool in VB but I cant get my speed over 30kbps. The speed when i use Filezilla, on the same machine with the same settings, is over 1000 Kbps.

The component is not yet registrated. Maby speed restrictions on the 30-day-trial?? I hope thats the case.

asked Nov 26 '12 at 11:10

esdeve's gravatar image


Here's the Chilkat SSH/SFTP v9.4.0 ActiveX (pre-release)



answered Nov 26 '12 at 16:50

chilkat's gravatar image

chilkat ♦♦

The problem is not due to the 30-day trial. It is most likely do to the TCP socket send buffer size. See SoSndBuf and SoRcvBuf Properties

Chilkat v9.4.0 will have two new properties (SoSndBuf and SoRcvBuf) for setting the socket send/receive buffer sizes. These properties have been added to each API that uses TCP socket communications (FTP, SMTP, POP3, IMAP, SSH, SFTP, HTTP, etc.) Other customers with the same problem have solved the issue by setting the SoSndBuf. (See SoSndBuf and SoRcvBuf Properties for more information)

I can provide a pre-release v9.4.0 download if you tell me which is needed (ActiveX, .NET, C++ libs, etc.)


answered Nov 26 '12 at 11:27

chilkat's gravatar image

chilkat ♦♦

thnx for the quick answer. Im glad to hear other customers have the same problems and that you can provide a solution for it.

I will need/try the ActiveX version



answered Nov 26 '12 at 16:30

esdeve's gravatar image


I used the pre-release v9.4.0 and the upload speed is now max 210 Kbps. Still not the 1 mbps when i use filezilla but more acceptable then the 30 kbps in the previous version.

I've set the so_sndbuf on 262144. any higher wont make a difference.

Any more advice to speed it up?


answered Nov 27 '12 at 04:08

esdeve's gravatar image


How are you uploading the files? Is it via a single call to UploadFileByName, or are you doing something different?

(Nov 27 '12 at 08:01) chilkat ♦♦

it is via UploadFileByName

(Nov 27 '12 at 08:31) esdeve

I don't know why the performance would be significantly different than FileZilla. I've always found that Chilkat performs roughly the same as FileZilla. You might look in the LastErrorText for clues. The LastErrorText always has information, even for successful method calls.

(Nov 27 '12 at 11:49) chilkat ♦♦

Is there an upper limit to the buffer sizes? I've read that the server could possibly reject the connection if the sosndbuf is too large and there is a low latency connection.


answered Dec 26 '13 at 16:55

zjeezy's gravatar image


I think it would be best to start a new question, since this isn't an answer to the original question that has already been marked answered.

Also, it would be helpful to provide any link(s) that you found where you read that a server could reject connections based on the sosndbuf size. It will save time for anyone trying to help you.

(Dec 26 '13 at 18:41) jpbro ♦
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Asked: Nov 26 '12 at 11:10

Seen: 3,854 times

Last updated: Dec 26 '13 at 18:41

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