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https://issues.apache.org/jira/browse/NET-493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13538976#comment-13538976
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Lee Albas commented on NET-493:
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I've come across this as well. It might be a deeper underlying issue with Java
7 (or, worst case, my issue differs from yours). Are you using Java 7? My FTP
code functions just fine in Java 6 whether I use the Apache Commons Net or Sun
Net libraries, but when I switch to Java 7, both slow down dramatically (about
100 times slower, e.g. 800Kb/s in J6 becomes 8.0KB/s in J7). As you've already
done, setting the buffer state to 0 returned things to normal for the Apache
library. Unfortunately, for the Java 7 Sun lib, there was no similar setting.
Profiling my program I detect that it spent an inordinate amount of time
executing within the Sun RMI-TCP section; perhaps that's where the underlying
problem lies.
Thanks for putting this on watch!
> FTPClient: Slow data transfer rate if __bufferSize != 0
> -------------------------------------------------------
>
> Key: NET-493
> URL: https://issues.apache.org/jira/browse/NET-493
> Project: Commons Net
> Issue Type: Bug
> Components: FTP
> Affects Versions: 3.2
> Environment: Windows 7 32bit / Windows XP 32bit
> Reporter: Mico Micic
> Labels: ftpclient
> Attachments: screenshot-1.jpg, screenshot-2.jpg
>
>
> The patch applied in [NET-465|https://issues.apache.org/jira/browse/NET-465]
> causes a very slow data transfer rate. The line {code}850:
> socket.setSendBufferSize(__bufferSize){code} in
> {code}_openDataConnection_{code} sets the buffer size to 1024 by default.
> With this size I had a very bad transfer rate on windows 7 and XP. The
> wireshark log shows that each FTP-DATA packet is exactly 1024 bytes long and
> has to be acknowledged on the TCP layer before the next one is sent. I don't
> know why, but when I set the buffer size to 0 (FTPClient.setBufferSize) the
> transfer rate is fine.
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