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FTPClient hangs when downloading large files

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Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540

FTPClient hangs when downloading large files

I'm using the net-commons v2.2 FTPClient to download files from a server
and it works great for files less then 250MB, but hangs with larger
files.
Wondering if there is anything I can do to get around this issue. I'm
downloading files up to 500MB in size.
Thanks in advance.

Here is my source code:
------------------------------------------------------------------------

FTPClient ftpClient = new FTPClient();
File file = null;

//
////////////////////////////////////////////////////////////////////
// Grab all files from the FTP server and place them in
the specified
// folder for processing.

////////////////////////////////////////////////////////////////////////

// Log on to FTP server
try {
// FTP Server
ftpClient.enterLocalPassiveMode();
ftpClient.connect(ftpServer);

// After connection attempt, you should
check the reply code to verify
// success.
int reply = ftpClient.getReplyCode();
if
(!FTPReply.isPositiveCompletion(reply))
{
ftpClient.disconnect();
logger.error("FTP server refused
connection.");
System.exit(1);
}

ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
ftpClient.login(m_sFTPCredUN,
m_sFTPCredPW);

} catch (java.net.ConnectException ex1) {

logger.info(ex1.getMessage());
System.out.print("-----FTP Connection
problem: "+ ftpServer+"\n");
return;
}catch (Exception ex1) {

logger.info(ex1.getMessage());
System.out.print("-----FTP Connection
problem: "+ftpServer+"\n");
return;
}

//Download files
FileOutputStream fos=null;
try {
// List the files in the directory
FTPFile[] files =
ftpClient.listFiles(ftpPath);
logger.info("Number of files in dir: " +
files.length);
for (int i = 0; i < files.length; i++) {
String fileName =
files[i].getName();

// ////////////////
// Get Files
// ////////////////
logger.info("Getting file: " +
fileName);
file = new
File(m_sInputRapierPath + File.separator
+
files[i].getName());
fos = new
FileOutputStream(file);

ftpClient.retrieveFile(ftpPath +
"/" + files[i].getName(),fos); //Hangs here
logger.info("File transfer
complete");
fos.close();

}

} catch
(org.apache.commons.net.io.CopyStreamException e) {
logger.info("FTP FETCH PROBLEM(1): " +
e.getMessage());
//System.out.println("FTP FETCH
PROBLEM(1): " + e.getMessage());
try {
if (file != null){
fos.close();
file.delete();
}
}//try
catch(IOException ex){
logger.info("FTP Problem
occured(4) : " + ex.getMessage());
}//catch

} catch (Exception ex) {
logger.info("FTP FETCH PROBLEM(3): " +
ex.getMessage());
//System.out.println("FTP FETCH
PROBLEM(3): " + e.getMessage());
try {
if (file != null){
fos.close();
file.delete();
}
}//try
catch(IOException ex1){
logger.info("FTP Problem
occured(4) : " + ex1.getMessage());
}//catch
} finally {
try {
if (file != null){

// Logout from the FTP
Server and disconnect
ftpClient.logout();

if(ftpClient.isConnected())

ftpClient.disconnect();
}
}//try
catch(IOException ex){
logger.info("FTP Problem
occured(4) : " + ex.getMessage());
}//catch
}//finally

}// if

sebb-2-2

Re: FTPClient hangs when downloading large files

Can you create a thread dump [1] to show where the code is hanging?

[1] http://www.crazysquirrel.com/computing/java/basics/java-thread-dump.jspx

On 15 February 2011 21:50, Cysneros, Nelson A CIV
SPAWARSYSCEN-PACIFIC, 56540 <[hidden email]> wrote:

>
>
> I'm using the net-commons v2.2 FTPClient to download files from a server
> and it works great for files less then 250MB, but hangs with larger
> files.
> Wondering if there is anything I can do to get around this issue. I'm
> downloading files up to 500MB in size.
> Thanks in advance.
>
> Here is my source code:
> ------------------------------------------------------------------------
>
> FTPClient ftpClient = new FTPClient();
> File file = null;
>
> //
> ////////////////////////////////////////////////////////////////////
> // Grab all files from the FTP server and place them in
> the specified
> // folder for processing.
>
> ////////////////////////////////////////////////////////////////////////
>
> // Log on to FTP server
> try {
> // FTP Server
> ftpClient.enterLocalPassiveMode();
> ftpClient.connect(ftpServer);
>
> // After connection attempt, you should
> check the reply code to verify
> // success.
> int reply = ftpClient.getReplyCode();
> if
> (!FTPReply.isPositiveCompletion(reply))
> {
> ftpClient.disconnect();
> logger.error("FTP server refused
> connection.");
> System.exit(1);
> }
>
> ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
> ftpClient.login(m_sFTPCredUN,
> m_sFTPCredPW);
>
> } catch (java.net.ConnectException ex1) {
>
> logger.info(ex1.getMessage());
> System.out.print("-----FTP Connection
> problem: "+ ftpServer+"\n");
> return;
> }catch (Exception ex1) {
>
> logger.info(ex1.getMessage());
> System.out.print("-----FTP Connection
> problem: "+ftpServer+"\n");
> return;
> }
>
> //Download files
> FileOutputStream fos=null;
> try {
> // List the files in the directory
> FTPFile[] files =
> ftpClient.listFiles(ftpPath);
> logger.info("Number of files in dir: " +
> files.length);
> for (int i = 0; i < files.length; i++) {
> String fileName =
> files[i].getName();
>
> // ////////////////
> // Get Files
> // ////////////////
> logger.info("Getting file: " +
> fileName);
> file = new
> File(m_sInputRapierPath + File.separator
> +
> files[i].getName());
> fos = new
> FileOutputStream(file);
>
> ftpClient.retrieveFile(ftpPath +
> "/" + files[i].getName(),fos); //Hangs here
> logger.info("File transfer
> complete");
> fos.close();
>
> }
>
>
>
> } catch
> (org.apache.commons.net.io.CopyStreamException e) {
> logger.info("FTP FETCH PROBLEM(1): " +
> e.getMessage());
> //System.out.println("FTP FETCH
> PROBLEM(1): " + e.getMessage());
> try {
> if (file != null){
> fos.close();
> file.delete();
> }
> }//try
> catch(IOException ex){
> logger.info("FTP Problem
> occured(4) : " + ex.getMessage());
> }//catch
>
> } catch (Exception ex) {
> logger.info("FTP FETCH PROBLEM(3): " +
> ex.getMessage());
> //System.out.println("FTP FETCH
> PROBLEM(3): " + e.getMessage());
> try {
> if (file != null){
> fos.close();
> file.delete();
> }
> }//try
> catch(IOException ex1){
> logger.info("FTP Problem
> occured(4) : " + ex1.getMessage());
> }//catch
> } finally {
> try {
> if (file != null){
>
> // Logout from the FTP
> Server and disconnect
> ftpClient.logout();
>
> if(ftpClient.isConnected())
>
> ftpClient.disconnect();
> }
> }//try
> catch(IOException ex){
> logger.info("FTP Problem
> occured(4) : " + ex.getMessage());
> }//catch
> }//finally
>
> }// if
>
>

sebb-2-2

Re: FTPClient hangs when downloading large files

In reply to this post by Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540

On 16 February 2011 01:43, Daniel F. Savarese <[hidden email]> wrote:

>
> In message <[hidden email].
> navy.mil>, "Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540" writes:
>>I'm using the net-commons v2.2 FTPClient to download files from a server
>>and it works great for files less then 250MB, but hangs with larger
>>files.
> ...
>>ftpClient.retrieveFile(ftpPath + "/" + files[i].getName(),fos); //Hangs here
>
> Try using retrieveFileStream and writing your own stream-copying loop
> (it should be only a few lines of code; but don't forget to call
> completePendingCommand afterward). If it works, then there's
> something wrong with org.apache.commons.net.io.Util.copyStream. If
> you still experience a mysterious hang, then it's probably
> not a Commons Net issue, but something to do with the network
> environment.

BTW, I tried running your code with an ISO of 654604 KB and it worked
fine for me.

> daniel
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [hidden email]
> For additional commands, e-mail: [hidden email]
>
>

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Steve Cole-6

RE: FTPClient hangs when downloading large files

In reply to this post by Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540

Try it with some other FTP client software. If it doesn't work, then the
problem isn't in your java class.

-----Original Message-----
From: Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540
[mailto:[hidden email]]
Sent: Tuesday, February 15, 2011 4:50 PM
To: [hidden email]
Subject: FTPClient hangs when downloading large files

I'm using the net-commons v2.2 FTPClient to download files from a server
and it works great for files less then 250MB, but hangs with larger
files.
Wondering if there is anything I can do to get around this issue. I'm
downloading files up to 500MB in size.
Thanks in advance.

Here is my source code:
------------------------------------------------------------------------

FTPClient ftpClient = new FTPClient();
File file = null;

//
////////////////////////////////////////////////////////////////////
// Grab all files from the FTP server and place them in
the specified
// folder for processing.

////////////////////////////////////////////////////////////////////////

// Log on to FTP server
try {
// FTP Server
ftpClient.enterLocalPassiveMode();
ftpClient.connect(ftpServer);

// After connection attempt, you should
check the reply code to verify
// success.
int reply = ftpClient.getReplyCode();
if
(!FTPReply.isPositiveCompletion(reply))
{
ftpClient.disconnect();
logger.error("FTP server refused
connection.");
System.exit(1);
}

ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
ftpClient.login(m_sFTPCredUN,
m_sFTPCredPW);

} catch (java.net.ConnectException ex1) {

logger.info(ex1.getMessage());
System.out.print("-----FTP Connection
problem: "+ ftpServer+"\n");
return;
}catch (Exception ex1) {

logger.info(ex1.getMessage());
System.out.print("-----FTP Connection
problem: "+ftpServer+"\n");
return;
}

//Download files
FileOutputStream fos=null;
try {
// List the files in the directory
FTPFile[] files =
ftpClient.listFiles(ftpPath);
logger.info("Number of files in dir: " +
files.length);
for (int i = 0; i < files.length; i++) {
String fileName =
files[i].getName();

// ////////////////
// Get Files
// ////////////////
logger.info("Getting file: " +
fileName);
file = new
File(m_sInputRapierPath + File.separator
+
files[i].getName());
fos = new
FileOutputStream(file);

ftpClient.retrieveFile(ftpPath +
"/" + files[i].getName(),fos); //Hangs here
logger.info("File transfer
complete");
fos.close();

}

} catch
(org.apache.commons.net.io.CopyStreamException e) {
logger.info("FTP FETCH PROBLEM(1): " +
e.getMessage());
//System.out.println("FTP FETCH
PROBLEM(1): " + e.getMessage());
try {
if (file != null){
fos.close();
file.delete();
}
}//try
catch(IOException ex){
logger.info("FTP Problem
occured(4) : " + ex.getMessage());
}//catch

} catch (Exception ex) {
logger.info("FTP FETCH PROBLEM(3): " +
ex.getMessage());
//System.out.println("FTP FETCH
PROBLEM(3): " + e.getMessage());
try {
if (file != null){
fos.close();
file.delete();
}
}//try
catch(IOException ex1){
logger.info("FTP Problem
occured(4) : " + ex1.getMessage());
}//catch
} finally {
try {
if (file != null){

// Logout from the FTP
Server and disconnect
ftpClient.logout();

if(ftpClient.isConnected())

ftpClient.disconnect();
}
}//try
catch(IOException ex){
logger.info("FTP Problem
occured(4) : " + ex.getMessage());
}//catch
}//finally

}// if

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Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540

RE: FTPClient hangs when downloading large files

Thank you everyone for such quick responses. I wanted to make sure I
follow up with more info when I had it, so here is what I know:

I'm able to download the files using Filezilla. Here is the
command/respond stack:

Command: RETR
15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
Response: 150 RETR command started
Response: 221 Goodbye - idle time exceeded
Error: Connection closed by server
Response: 550 RETR failed...
Error: File transfer failed after transferring 302.9 MB in 3650 seconds
Status: Starting download of
/week0308/15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
Command: PASV
Response: 227 Entering Passive Mode (173,166,178,236,217,144).
Command: REST 302821425
Response: 350 Restarting at 302821425
Command: RETR
15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
Response: 150 RETR command started
Response: 226 Transfer Complete
Status: File transfer successful, transferred 4.9 MB in 58 seconds

It seems that the server is timing out the connection, while the file is
still downloading. Filezilla seems to restart the download where it left
off and continues.

From the commons-net documentation, it seems that I should get an
FTPConnectionClosedException when this happens. I then could restart
the download also, but I never get any exception, my application always
hangs using the "retrieveFile" function.

I then tried using the "retrieveFileStream" function but that also hangs
in the following locations.

If you call the completePendingCommand immediately after the
retrieveFileStream function, then it will hang at the
completePendingCommand function.
------------------------------------------------------------------------
----
InputStream ios = ftpClient.retrieveFileStream(fileName);
boolean commandOK=ftpClient.completePendingCommand(); //Hangs here

//write the inputStream to a FileOutputStream
OutputStream out = new FileOutputStream(file);

fos.flush();
fos.close();

int read = 0;
byte[] bytes = new byte[1024];

while ((read = ios.read(bytes)) != -1) {
out.write(bytes, 0, read);
}
------------------------------------------------------------------------
--------

If you call the completePendingCommand after the while loop to read the
ios, then it will hang during the while loop.
------------------------------------------------------------------------
----
InputStream ios = ftpClient.retrieveFileStream(fileName);

//write the inputStream to a FileOutputStream
OutputStream out = new FileOutputStream(file);

fos.flush();
fos.close();

int read = 0;
byte[] bytes = new byte[1024];

while ((read = ios.read(bytes)) != -1) { //Hangs here
out.write(bytes, 0, read);
}

boolean commandOK=ftpClient.completePendingCommand();
------------------------------------------------------------------------
--------

I probably could get the FTP server admins to bump up the timout time,
but it would be nice to get this to work regardless.

Thanks again for all the advice.

-----Original Message-----
From: Steve Cole [mailto:[hidden email]]
Sent: Wednesday, February 16, 2011 4:59 AM
To: 'Commons Users List'
Subject: RE: FTPClient hangs when downloading large files

Try it with some other FTP client software. If it doesn't work, then the
problem isn't in your java class.

-----Original Message-----
From: Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540
[mailto:[hidden email]]
Sent: Tuesday, February 15, 2011 4:50 PM
To: [hidden email]
Subject: FTPClient hangs when downloading large files

I'm using the net-commons v2.2 FTPClient to download files from a server
and it works great for files less then 250MB, but hangs with larger
files.
Wondering if there is anything I can do to get around this issue. I'm
downloading files up to 500MB in size.
Thanks in advance.

Here is my source code:
------------------------------------------------------------------------

FTPClient ftpClient = new FTPClient();
File file = null;

//
////////////////////////////////////////////////////////////////////
// Grab all files from the FTP server and place them in
the specified
// folder for processing.

////////////////////////////////////////////////////////////////////////

// Log on to FTP server
try {
// FTP Server
ftpClient.enterLocalPassiveMode();
ftpClient.connect(ftpServer);

// After connection attempt, you should
check the reply code to verify
// success.
int reply = ftpClient.getReplyCode();
if
(!FTPReply.isPositiveCompletion(reply))
{
ftpClient.disconnect();
logger.error("FTP server refused
connection.");
System.exit(1);
}

ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
ftpClient.login(m_sFTPCredUN,
m_sFTPCredPW);

} catch (java.net.ConnectException ex1) {

logger.info(ex1.getMessage());
System.out.print("-----FTP Connection
problem: "+ ftpServer+"\n");
return;
}catch (Exception ex1) {

logger.info(ex1.getMessage());
System.out.print("-----FTP Connection
problem: "+ftpServer+"\n");
return;
}

//Download files
FileOutputStream fos=null;
try {
// List the files in the directory
FTPFile[] files =
ftpClient.listFiles(ftpPath);
logger.info("Number of files in dir: " +
files.length);
for (int i = 0; i < files.length; i++) {
String fileName =
files[i].getName();

// ////////////////
// Get Files
// ////////////////
logger.info("Getting file: " +
fileName);
file = new
File(m_sInputRapierPath + File.separator
+
files[i].getName());
fos = new
FileOutputStream(file);

ftpClient.retrieveFile(ftpPath +
"/" + files[i].getName(),fos); //Hangs here
logger.info("File transfer
complete");
fos.close();

}

} catch
(org.apache.commons.net.io.CopyStreamException e) {
logger.info("FTP FETCH PROBLEM(1): " +
e.getMessage());
//System.out.println("FTP FETCH
PROBLEM(1): " + e.getMessage());
try {
if (file != null){
fos.close();
file.delete();
}
}//try
catch(IOException ex){
logger.info("FTP Problem
occured(4) : " + ex.getMessage());
}//catch

} catch (Exception ex) {
logger.info("FTP FETCH PROBLEM(3): " +
ex.getMessage());
//System.out.println("FTP FETCH
PROBLEM(3): " + e.getMessage());
try {
if (file != null){
fos.close();
file.delete();
}
}//try
catch(IOException ex1){
logger.info("FTP Problem
occured(4) : " + ex1.getMessage());
}//catch
} finally {
try {
if (file != null){

// Logout from the FTP
Server and disconnect
ftpClient.logout();

if(ftpClient.isConnected())

ftpClient.disconnect();
}
}//try
catch(IOException ex){
logger.info("FTP Problem
occured(4) : " + ex.getMessage());
}//catch
}//finally

}// if

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sebb-2-2

Re: FTPClient hangs when downloading large files

On 21 March 2011 16:24, Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC,
56540 <[hidden email]> wrote:

> Thank you everyone for such quick responses. I wanted to make sure I
> follow up with more info when I had it, so here is what I know:
>
> I'm able to download the files using Filezilla. Here is the
> command/respond stack:
>
> Command: RETR
> 15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
> Response: 150 RETR command started
> Response: 221 Goodbye - idle time exceeded
> Error: Connection closed by server
> Response: 550 RETR failed...
> Error: File transfer failed after transferring 302.9 MB in 3650 seconds
> Status: Starting download of
> /week0308/15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
> Command: PASV
> Response: 227 Entering Passive Mode (173,166,178,236,217,144).
> Command: REST 302821425
> Response: 350 Restarting at 302821425
> Command: RETR
> 15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
> Response: 150 RETR command started
> Response: 226 Transfer Complete
> Status: File transfer successful, transferred 4.9 MB in 58 seconds
>
> It seems that the server is timing out the connection, while the file is
> still downloading. Filezilla seems to restart the download where it left
> off and continues.

What is the server software?

Seems to me the server is broken, because it should know that the
control channel won't normally be used until the data transfer is
finished.

[This is different from the keep-alive problem, which is where a
router times out a connection.]

> From the commons-net documentation, it seems that I should get an
> FTPConnectionClosedException when this happens. I then could restart
> the download also, but I never get any exception, my application always
> hangs using the "retrieveFile" function.

No, that Exception is generated if the control channel is unexpectedly
closed, which is not the case here.

> I then tried using the "retrieveFileStream" function but that also hangs
> in the following locations.

Have you set a data timeout?

That should at least prevent the code from hanging; you may then be
able to recover.

I don't suppose it's possible to get external (read-only) access to the server?

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Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540

RE: FTPClient hangs when downloading large files

Thank you!!! By putting in a time out I was able to catch the Exception and recover.

The FTP server is maintained off site, I asked them about the FTP server software they are using and if we can get a "Read Only" account set up for you but I have not heard back from them.
I'll pass along the info, when I get it.

Thanks again for your advice. Everything is working as expected now.

-----Original Message-----
From: sebb [mailto:[hidden email]]
Sent: Monday, March 21, 2011 11:17 AM
To: Commons Users List
Subject: Re: FTPClient hangs when downloading large files

On 21 March 2011 16:24, Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540 <[hidden email]> wrote:

> Thank you everyone for such quick responses. I wanted to make sure I
> follow up with more info when I had it, so here is what I know:
>
> I'm able to download the files using Filezilla. Here is the
> command/respond stack:
>
> Command: RETR
> 15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
> Response: 150 RETR command started
> Response: 221 Goodbye - idle time exceeded
> Error: Connection closed by server
> Response: 550 RETR failed...
> Error: File transfer failed after transferring 302.9 MB in 3650
> seconds
> Status: Starting download of
> /week0308/15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
> Command: PASV
> Response: 227 Entering Passive Mode (173,166,178,236,217,144).
> Command: REST 302821425
> Response: 350 Restarting at 302821425
> Command: RETR
> 15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
> Response: 150 RETR command started
> Response: 226 Transfer Complete
> Status: File transfer successful, transferred 4.9 MB in 58 seconds
>
> It seems that the server is timing out the connection, while the file
> is still downloading. Filezilla seems to restart the download where it
> left off and continues.

What is the server software?

Seems to me the server is broken, because it should know that the control channel won't normally be used until the data transfer is finished.

[This is different from the keep-alive problem, which is where a router times out a connection.]

> From the commons-net documentation, it seems that I should get an
> FTPConnectionClosedException when this happens. I then could restart
> the download also, but I never get any exception, my application
> always hangs using the "retrieveFile" function.

No, that Exception is generated if the control channel is unexpectedly closed, which is not the case here.

> I then tried using the "retrieveFileStream" function but that also
> hangs in the following locations.

Have you set a data timeout?

That should at least prevent the code from hanging; you may then be able to recover.

I don't suppose it's possible to get external (read-only) access to the server?

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sebb-2-2

Re: FTPClient hangs when downloading large files

On 23 March 2011 05:06, Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC,
56540 <[hidden email]> wrote:
> Thank you!!! By putting in a time out I was able to catch the Exception and recover.
>
> The FTP server is maintained off site, I asked them about the FTP server software they are using and if we can get a "Read Only" account set up for you but I have not heard back from them.
> I'll pass along the info, when I get it.

Thanks.

> Thanks again for your advice. Everything is working as expected now.

OK, thanks for updating us.

>
>
> -----Original Message-----
> From: sebb [mailto:[hidden email]]
> Sent: Monday, March 21, 2011 11:17 AM
> To: Commons Users List
> Subject: Re: FTPClient hangs when downloading large files
>
> On 21 March 2011 16:24, Cysneros, Nelson A CIV SPAWARSYSCEN-PACIFIC, 56540 <[hidden email]> wrote:
>> Thank you everyone for such quick responses. I wanted to make sure I
>> follow up with more info when I had it, so here is what I know:
>>
>> I'm able to download the files using Filezilla. Here is the
>> command/respond stack:
>>
>> Command: RETR
>> 15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
>> Response: 150 RETR command started
>> Response: 221 Goodbye - idle time exceeded
>> Error: Connection closed by server
>> Response: 550 RETR failed...
>> Error: File transfer failed after transferring 302.9 MB in 3650
>> seconds
>> Status: Starting download of
>> /week0308/15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
>> Command: PASV
>> Response: 227 Entering Passive Mode (173,166,178,236,217,144).
>> Command: REST 302821425
>> Response: 350 Restarting at 302821425
>> Command: RETR
>> 15MAR11WV010800011MAR15110220-P1BS-052429279010_04_P008.nitf
>> Response: 150 RETR command started
>> Response: 226 Transfer Complete
>> Status: File transfer successful, transferred 4.9 MB in 58 seconds
>>
>> It seems that the server is timing out the connection, while the file
>> is still downloading. Filezilla seems to restart the download where it
>> left off and continues.
>
> What is the server software?
>
> Seems to me the server is broken, because it should know that the control channel won't normally be used until the data transfer is finished.
>
> [This is different from the keep-alive problem, which is where a router times out a connection.]
>
>> From the commons-net documentation, it seems that I should get an
>> FTPConnectionClosedException when this happens. I then could restart
>> the download also, but I never get any exception, my application
>> always hangs using the "retrieveFile" function.
>
> No, that Exception is generated if the control channel is unexpectedly closed, which is not the case here.
>
>> I then tried using the "retrieveFileStream" function but that also
>> hangs in the following locations.
>
> Have you set a data timeout?
>
> That should at least prevent the code from hanging; you may then be able to recover.
>
> I don't suppose it's possible to get external (read-only) access to the server?
>
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