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From "Sebb (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (NET-406) Improved disconnect handling in FtpClient: retrieveFile never returns under certain conditions and calling FtpClient.disconnect does not terminate the transfer.
Date Tue, 03 May 2011 10:56:03 GMT

    [ https://issues.apache.org/jira/browse/NET-406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13028154#comment-13028154
] 

Sebb commented on NET-406:
--------------------------

Have you used FTPClient.setDataTimeout() to set a data timeout?

Does that work for some cases or none?

If none, then that needs to be investigated.

Not sure it's necessary to use a List<Socket>; as far as I can tell, there can be at
most one active data socket, which could be stored in a volatile field instead.

Also, I'm not sure that extending disconnect is the correct place to do this, as that also
terminates the control connection.

It might be better to provide a means to close the data socket directly.

> Improved disconnect handling in FtpClient: retrieveFile never returns under certain conditions
and calling FtpClient.disconnect does not terminate the transfer.
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: NET-406
>                 URL: https://issues.apache.org/jira/browse/NET-406
>             Project: Commons Net
>          Issue Type: Improvement
>          Components: FTP
>    Affects Versions: 2.0
>         Environment: Linux
>            Reporter: Nils Martin Sande
>              Labels: features
>
> During file download it is possible for the transfer to stop without any time out being
triggered in FtpClient. The result is a "lost" thread (it never returns from retrieveFile).
Calling interrupt on the missing thread does not do anything. 
> When we encountered this error we fist tried to monitor the downloaded file and then
call FtpClient.disconnect if the size on disk remained unchanged for a given period of time.
This did not solve the problem since FtpClient.disconnect does not close the socket used by
the transfer. Changing FtpClient so that it keeps track of active sockets and then closing
all active sockets on FtpClient.disconnect solved the problem for us. Although this error
is not very common, the ability to completely kill the connection including all transfers
seems like a useful feature. I have included the details of the modifications we made, maybe
someone will find them useful. If there is a better way to get around this please let me know.
> {code:title=FtpClient.java_retrieveFile|borderStyle=solid}
> //The modified retrieveFile method (__activeSockets is a synchronized List<Socket>)
> public boolean retrieveFile(String remote, OutputStream local)
>             throws IOException {
>         InputStream input;
>         Socket socket;
>         if ((socket = _openDataConnection_(FTPCommand.RETR, remote)) == null) {
>             return false;
>         }
>         __activeSockets.add(socket);
>         try {
>             input = new BufferedInputStream(socket.getInputStream(),
>                     getBufferSize());
>             if (__fileType == ASCII_FILE_TYPE) {
>                 input = new FromNetASCIIInputStream(input);
>             }
>             // Treat everything else as binary for now
>             try {
>                 Util.copyStream(input, local, getBufferSize(),
>                         CopyStreamEvent.UNKNOWN_STREAM_SIZE, null,
>                         false);
>             } catch (IOException e) {
>                 try {
>                     socket.close();
>                 } catch (IOException f) {
>                 }
>                 throw e;
>             }
>             socket.close();
>             return completePendingCommand();
>         } finally {
>             __activeSockets.remove(socket);
>         }
>     }
> //The modified disconnect method
> public void disconnect() throws IOException {
>         super.disconnect();
>         __initDefaults();
>         IOException exception = null;
>         for (Socket socket : __activeSockets) {
>             try {
>                 socket.close();
>             } catch (IOException ex) {
>                 exception = ex;
>             }
>         }
>         __activeSockets.clear();
>         if (exception != null) {
>             throw exception;
>         }
>     }
> {code}

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