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are there any limitations for the upload speed?

Dec 26 '13 at 18:41

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.

Accepted Answer

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


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.)


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



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?


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.