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https://issues.apache.org/jira/browse/NET-493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13545699#comment-13545699
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Erik Wramner commented on NET-493:
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I don't know if this is the root cause, but we have had severe performance
issues with FTP using commons-net 3.2. A file that normally takes seconds to
transfer may take more than an hour. We have observed that often the file is
transferred relatively quickly, but then it can take a very long time before
the response from the remote server that the file has been successfully
received reaches our code (and the logs in commons-net). Reverting to 3.1
solves the performance issues. We are using JDK 1.7_09 on Windows Server 2003.
> 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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