Re: CFtpFindFile freezes
On Sep 29, 4:25 pm, MRe <pgd...@gmail.com> wrote:
Hi,
Thank you for the response..
[short version]
Randomly, between CFtpFileFind::FindFile and looping
CFtpFileFind::FindNextFile, my internet FTP connection hangs. It is
less likely to hang if a Sleep(N) is added to the loop. The bigger N
is, the less likely it is to hang. Though large Ns is slowing the
program down too much. Any ideas what's going on?
****
First rule: if your multithreaded code doesn't work unless you add a Sl=
eep() call, your
design is wrong. You have not stated if this is multithreaded. Is=
it really the
CFtpFile::FindNextFile that hangs? Or is it something else? Since=
you haven't shown any
code, we are left to try to debug by psychic vibrations, never a viable=
solution.
****
Sorry, the application is not multi-threaded and does not use
asynchronous calls.
I have implemented a new high-speed logging mechanism (that doesn't
delay long enough to alter the results) and have found the exact line
of code that freezes to be ftpFind.FindFile("*.*");
Here is just the FTP code extracted from the actual code:
// This whole block of code loops for each unique log-in details
(distinct IPAddress, UserName, Password)
// {{
if(m_pInetSession != NULL)
delete m_pInetSession;
m_pInetSession = new CInternetSession
( m_LogType
, 1
, PRE_CONFIG_INTERNET_ACCESS
, NULL
, NULL
, INTERNET_FLAG_DONT_CACHE
);
m_pFtpConnection = m_pInetSession->GetFtpConnection
( IPAddress
, UserName
, Password
);
...
// This block of code loops for each directory on the server
// {{
BOOL bContinue = ftpFind.FindFile ("*.*");
while (bContinue)
{
bContinue = ftpFind.FindNextFile();
...}
ftpFind.Close();
// }} END: This block of code loops for each directory on the server
...
m_pFtpConnection->Close( );
// }} END: This whole block of code loops for each unique log-in
details
This code could/would be better off like this:
1. declare session, connection and file as auto_ptr pointers
2. I don't know where ftpFind is coming from, but it should be local
to a function.
3. Is connection a member of some class? I don't see why. Session,
either.
{ // Block is intentional. It destroys objects when they are not
needed anymore,
// in good order.
CInternetSession session(
m_LogType
, 1
, PRE_CONFIG_INTERNET_ACCESS
, NULL
, NULL
, INTERNET_FLAG_DONT_CACHE
);
auto_ptr<CFtpConnection P(m_pInetSession->GetFtpConnection
( IPAddress
, UserName
, Password
));
CFtpFileFind ftpFind;
BOOL bContinue = ftpFind.FindFile ("*.*");
while (bContinue)
{
bContinue = ftpFind.FindNextFile();
// ...
}
}
I added code that writes a log entry immediately before and
immediately after each of these lines of code, and normally they all
execute instantly (within the resolution of the log's timer) but when
it fails, there's a log entry before { BOOL bContinue =
ftpFind.FindFile ("*.*"); } and then the one after is exactly
300000(+-16) milliseconds later, and then everything else fails until
the next connection is established. There are other FTP commands, like
setting directories, and putting and getting files, but logging shows
these don't need to execute for the problem to show itself (so I
haven't included them).
Try the code above and see if that works. It may be that you have a
problem with the FTP server, but from what I see so far in your code,
that's highly unlikely. I think that you have a pretty bad code and
that you need to clean it up.
My money is on all sorts of memory leaks which end up as handle leaks
in your own code. Remove all member variables (m_pInetSession,
m_pFtpConnection, ftpFind) from whatever class they are in and make
them local as I've shown you up here. Pass them to code that needs
them. By looking at the snippet you have, I'd say that the only thing
you'll ever need to pass around will be a CInternetFile that you'll
get from m_pFtpConnection->OpenFile, and you'll pass it around in line
"// ..." from the loop. Put said CInternetFile into an auto_ptr, too.
If you don't know why I am bothering you about auto_ptr, read about
exception safety and RAII (e.g. on Wikipedia).
Goran.