On Wed, 5 May 2010, Xu, Qiang (FXSGSC) wrote:

> I seem to have found the reason by comparing the two traces captured when
> using libcurl and when using sftp_write_nonblock:

You make me tired. I already suggested EXACTLY this test several emails ago.

> The constant is tentatively changed to 8192 (half of 16KB), and the change
> makes the difference. The transfer to the SFTP server succeeds! So, it seems
> that this Reflection server has a stricter/smaller buffer size requirement.

So the problem is then most likely in the server end, as I don't believe
libssh2 ever uses any illegal packet sizes. You could of course try the
non-blocking libssh2 SFTP example snippet with a 16KB buffer to see what
happens. If this theory holds, it should fail...

> Tomorrow, I'll tried to increase it to 12KB to see whether it still works. I
> want to increase the buffer size to as big a value as possible, to enhance
> the transfer speed.

I would also encourage you to contact whoever makes that SFTP server and
confront them with these facts and ask them about specific details on why it
says/does this and what we and they can do about the situation. Building a
custom libcurl with a smaller buffer may be a solution for you, right now, but
it certainly is not even a half-baked work-around for the long term - and I'm
in this game long term...

-- 
  / daniel.haxx.se
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