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Re: How to do optimal FTP upload for multiple files?

From: Daniel Jeliński via curl-library <>
Date: Wed, 17 Jul 2019 21:59:18 +0200

> Slowness was reported by few users on Windows 10 x64. Slowness (and, in other case, timeouts) were reported against couple of totally different FTP servers around the globe. At least 5 different (from my user's logs) servers run by different companies, so unfortunately there's no way to blame them here. Only my use of libcurl.

Hi Taras,
Long time ago when I was tuning curl behavior on Windows, we found
that Windows running on Virtualbox with network adapter mode set to
NAT (the default) does not provide us with the optimal buffer size,
and upload speeds suffer because of that [1]. Back then, switching
Virtualbox to bridged adapter mode allowed curl to work at expected

This problem only happens for programs using non-blocking sockets,
which may explain why other programs manage to run fast.

Let me know if that helps.



Received on 2019-07-17