Hi,
I was encountering this problem.
Thank you very much for fixing the code.
BTW, part of the reason for this problem is synchronized
conList, accessed by timerTask() and newConnection().
When servSoc.accept() blocks, conList is kept locked by
timerTask() until servSoc.accept() returns.
So newConnection() has to wait, because conList.add()
is synchronized.
I guess it's better that timerTask() iterates over
"clone" of conList, than synchronizes on it.
How do you think?
Thanks,
OZAKI Ittetsu
On Mon, 24 Apr 2006 03:14:06 -0700 (PDT)
Rana Bhattacharyya <[EMAIL PROTECTED]> wrote:
> Hi,
>
> Thank you very much for replying. You are absolutely
> right. I shall add one data connection configuration
> parameter to set the server socket timeout. Basically
> I shall set the SO_TIMEOUT.
>
> FtpDataConnection is not shared in multiple
> connections. Each ftp session has a FtpDataConnection
> instance. So other client can open data connection
> when server is waiting for one client.
>
> These are synchronized because, the FTP session
> cleaner removes idle connections at specified interval
> and this timer thread can mess-up if these methods are
> not synchronized.
>
> Thanks,
> Rana Bhattacharyya
>
>
> --- Jens Viebig <[EMAIL PROTECTED]> wrote:
>
> > I did some more testing and the two functions i
> > pointed out do no harm and
> > return immediately.
> > The function that is causing the hang is in
> > FtpDataConnection as you pointed
> > out:
> >
> > public synchronized Socket getDataSocket() {
> > ...
> > m_dataSoc = m_servSoc.accept();
> > ...
> > }
> >
> > Yes i would definetely add a timeout for m_servSoc.
> >
> > Without a timeout this function waits forever, when
> > the data connection is
> > not established. This is not good and there are
> > several reasons why this
> > coud happen (Server side-firewalls, client-side
> > firewalls, broken ftp
> > clients,broken network connections...).
> >
> > Does this function have to be synchronized ? Even
> > with a timeout for the
> > server socket, while the server waits for the
> > incoming data connection, no
> > other client can connect to the server.
> >
> > ----- Original Message -----
> > From: "Rana Bhattacharyya" <[EMAIL PROTECTED]>
> > To: <[email protected]>
> > Sent: Monday, April 24, 2006 7:17 AM
> > Subject: Re: Bug, Server locks up because of
> > firewall issues
> >
> >
> > > Hi,
> > >
> > > new RequestHandler() handles the new connection.
> > It
> > > does not handle the passive mode data transfer.
> > > FtpDataConnection class handles all data
> > connections
> > > (both active and passive). So you are suggesting
> > to
> > > close the passive server socket if there is no
> > client
> > > connections within a speified time to prevent
> > server
> > > lock out. Please write your comments.
> > >
> > > Thanks,
> > > Rana Bhattacharyya
> > >
> > >
> > > --- Jens Viebig <[EMAIL PROTECTED]> wrote:
> > >
> > >> Hi List,
> > >> I found a situation where the ftp server locks up
> > >> and no new connections can be made.
> > >> ftpserver runs behind a firewall with open port
> > 21
> > >> and runs fine with clients working in active
> > mode.
> > >> When a client tries to connect in passive mode,
> > the
> > >> data connection is blocked by the firewall. This
> > is
> > >> the point where the server locks up. It seems
> > that
> > >> the server is waiting for the incoming data
> > >> connection that is never established because of
> > the
> > >> firewall.
> > >>
> > >> The main thread executes two functions after
> > >> accepting the client socket connection
> > >>
> > >> IConnection connection = new
> > >> RequestHandler(m_ftpConfig, soc);
> > >> conManager.newConnection(connection);
> > >>
> > >> it seems that one of the functions causes the
> > >> hangup. In my understanding of server
> > architecture
> > >> the thread handling the client connection should
> > be
> > >> forked immediately after the accept() of the
> > socket
> > >> or the functions should have a very short
> > timeout,
> > >> because no new connections can be established
> > while
> > >> these functions are executed.
> > >>
> > >>
> > >>
> > >>
> > >
> > >
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>
>
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