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From "Anil Gaddipati (JIRA)" <j...@apache.org>
Subject [jira] Commented: (NET-61) [net] FTPClient.listFiles() hangs on Red Hat Linux
Date Fri, 17 Sep 2010 15:20:36 GMT

    [ https://issues.apache.org/jira/browse/NET-61?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12910622#action_12910622
] 

Anil Gaddipati commented on NET-61:
-----------------------------------

Llooks like this is an issue between FtpClient(on Linux servers) and FTPServer
 
FtpClient from Linux hangs after certain point of time. Because of unusual nature of communication
between ftp Client(in this case its Linux) and Server certain port numbers should be open
on Client (Linux server) for ftp Server to send back data. But due to firewall restrictions
most of these unprivileged ports are closed on Linux. 
Apparently it looks like ftp Server uses a different port each time a request comes from ftp
Client, some of which are not open on Linux. 
 
The solution is Ftp Client to enter "passive" (PASV) mode. In passive mode Ftp Client (on
Linux) opens a dedicated port for server to send back data.
I have verified these changes on NewMedia Stage and its working

FtpClient.enterLocalPassiveMode()

You can read more http://slacksite.com/other/ftp.html


> [net] FTPClient.listFiles() hangs on Red Hat Linux
> --------------------------------------------------
>
>                 Key: NET-61
>                 URL: https://issues.apache.org/jira/browse/NET-61
>             Project: Commons Net
>          Issue Type: Bug
>          Components: FTP
>    Affects Versions: 1.4
>         Environment: Operating System: Linux
> Platform: PC
>            Reporter: George Van Treeck
>            Priority: Blocker
>
> A Java app that uses FTPClient to download a file from a website to Windows XP 
> works properly. But, when the same app runs on Linux to download the same file 
> from the same website, it hangs at listFiles().
> Using Java 1.5.0_03 on both the Windows XP and Linux. The version of Linux 
> used is Fedor Red Hat Linux Core 3 with all the latest updates. The following 
> segment of code from the program demonstrates the problem:
>               FTPClient ftp = new FTPClient();
>               ftp.connect(host);
>               reply = ftp.getReplyCode();
>               if (!FTPReply.isPositiveCompletion(reply)) {
>                 final String ftpStatus = ftp.getReplyString();
>                 ftp.disconnect();
>                 throw new IOException(
>                     "FTP server refused connection. Status: " +
>                    ftpStatus);
>               }
>               ftp.login(user, password);
>               reply = ftp.getReplyCode();
>               if (!FTPReply.isPositiveCompletion(reply)) {
>                 final String ftpStatus = ftp.getReplyString();
>                 ftp.disconnect();
>                 throw new IOException(
>                     "FTP server refused username/password. Status: " +
>                    ftpStatus);
>               }
>               String[] list = ftp.listNames();

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