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From sebb <seb...@gmail.com>
Subject Re: [NET] FTP Connection occasionally hangs on listFiles()
Date Mon, 10 Sep 2012 22:33:05 GMT
On 10 September 2012 08:09, Johannes Frank <Johannes.Frank@kisters.de> wrote:
> Hello together.
>
> I have a weird problem which unfortunately leads to production halts at
> two of our customers so I urge for a pointer in the right direction here.
>
> My software periodically detects files on a FTP Server and downloads them.
> This works fine for some time but quite randomly, out of a suddin this
> loop starts to hang indefinitely until manually killed and restarted by
> the Administrator.
>
> I narrowed it down so far that I can say that the FTPClient.listFiles()
> method hangs and never returns. Here is what the ftp communication log
> says on a normal run:
>
> 2012-09-04T12:41:01.130Z DEBUG [location.FtpLocation.protocolCommandSent]
> Veribox A-Dateien: --> NOOP
> 2012-09-04T12:41:01.132Z DEBUG
> [location.FtpLocation.protocolReplyReceived] Veribox A-Dateien: <-- 200
> Command okay.
> 2012-09-04T12:41:01.132Z DEBUG [location.FtpLocation.protocolCommandSent]
> Veribox A-Dateien: --> PASV
> 2012-09-04T12:41:01.140Z DEBUG
> [location.FtpLocation.protocolReplyReceived] Veribox A-Dateien: <-- 227
> Entering Passive Mode (172,35,1,12,7,70
> )
> 2012-09-04T12:41:01.141Z DEBUG [location.FtpLocation.protocolCommandSent]
> Veribox A-Dateien: --> LIST *
> 2012-09-04T12:41:01.146Z DEBUG
> [location.FtpLocation.protocolReplyReceived] Veribox A-Dateien: <-- 150
> Opening ASCII mode data connection for
> /bin/ls.
> 2012-09-04T12:41:01.186Z DEBUG
> [location.FtpLocation.protocolReplyReceived] Veribox A-Dateien: <-- 226
> Transfer complete. 117 bytes transferre
> d. 7,14 KB/sec.
>
> And here is what it says the moment it hangs up:
>
> 2012-09-04T12:41:51.196Z DEBUG [location.FtpLocation.protocolCommandSent]
> Veribox A-Dateien: --> NOOP
> 2012-09-04T12:41:51.197Z DEBUG
> [location.FtpLocation.protocolReplyReceived] Veribox A-Dateien: <-- 200
> Command okay.
> 2012-09-04T12:41:51.198Z DEBUG [location.FtpLocation.protocolCommandSent]
> Veribox A-Dateien: --> PASV
> 2012-09-04T12:41:51.204Z DEBUG
> [location.FtpLocation.protocolReplyReceived] Veribox A-Dateien: <-- 227
> Entering Passive Mode (172,35,1,12,7,71
> )
> 2012-09-04T12:41:51.205Z DEBUG [location.FtpLocation.protocolCommandSent]
> Veribox A-Dateien: --> LIST *
> 2012-09-04T12:41:51.211Z DEBUG
> [location.FtpLocation.protocolReplyReceived] Veribox A-Dateien: <-- 150
> Opening ASCII mode data connection for
> /bin/ls.
>
> As you can see, the server answers that it's opening an ascii mode data
> connection but then nothing seems to happen.
>
> This is what netstat -np says:
> tcp       91      0 172.30.3.21:39009       172.35.1.12:2730 CLOSE_WAIT
> 24094/java
> tcp        0      0 172.30.3.21:45273       172.35.1.12:1863 ESTABLISHED
> 24094/java
> tcp        0      0 172.30.3.21:56584       172.35.1.12:2299 ESTABLISHED
> 24094/java
> tcp        0      0 172.30.3.21:53582       172.35.1.12:2730 ESTABLISHED
> 24094/java
> tcp        0      0 172.30.3.21:57945       172.35.1.12:2730 ESTABLISHED
> 24094/java
> tcp       95      0 172.30.3.21:39010       172.35.1.12:2730 CLOSE_WAIT
> 24094/java
>
> 2730 is the control port of the ftp server, 2299, 1863 are data
> connections. Note the non-empty Send-Q for the CLOSE_WAIT connections.
>
> The issue I have here seems to be relatively independent of everything I
> can come up with.
> We have this problem in both linux (SuSE 11.4 64bit) and Windows XP, The
> FTP server being once a Serv-U under Windows 2003 Standard and vsftp under
> linux. The java virtual machine is openjdk under linux and sun java 6
> under windows. As far as I can see, no proxies or firewalls are in the way
> on either of the customers systems. I tested with both commons-net 2.0 and
> 3.1 with no difference in result.
>
> Did anyone on this list ever encounter an issue like this before and is
> there a way to circumvent this stalling of the listFiles() call?

If you can provide a sample program that reproduces the problem, then
please raise a JIRA issue and attach the code and sample output from
the run.
Make sure you enable command logging.

> Kind regards,
> Johannes Frank
> --------------------------------------------------------------------------------------------------------------------------------------------
> Johannes Frank - KISTERS AG - Charlottenburger Allee 5 - 52068 Aachen - Germany
> Handelsregister Aachen, HRB-Nr. 7838 | Vorstand: Klaus Kisters, Hanns Kisters | Aufsichtsratsvorsitzender:
Dr. Thomas Klevers
> Phone: +49 241 9671 -0 | Fax: +49 241 9671 -555 | E-Mail: Johannes.Frank@kisters.de |
WWW:
> --------------------------------------------------------------------------------------------------------------------------------------------
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