Re: Theads and FTP
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On Mon, 5 Dec 2011, Arne Vajh??j wrote:
On 12/5/2011 9:58 AM, Andreas Leitgeb wrote:
Arne Vajh??j<arne@vajhoej.dk> wrote:
On 12/4/2011 4:14 PM, Daniel Pitts wrote:
On 12/3/11 8:31 PM, Roedy Green wrote:
I have watched FTP voyager work. It seems to have at least two threads
simultaneously uploading downloading. You might think what's the
point. You can be transferring while you are waiting for the server
to open or close a file and send back confirmation.
I was wondering if this is done by logging on twice and having two
completely independent sessions, or if FTP itself has some multithread
ability.
Why not look up the RFC on the FTP protocol? I seem to recall that it
inherently uses two sockets, one for the commands and one for
transfers. I don't know if the command stream is allowed (or
expected) to be active during a transfer, I haven't read the spec
myself in quite a while. Also, you don't necessarily need multiple
threads to handle multiple connections. In posix c "select()" is use
to manage multiple connections.
I believe it is possible to write a FTP client single threaded even
without select.
Ok there's of course also poll(), and one could set all channels to
non-blocking mode and do a more or less(with sleep) busy loop iterating
through all the channels and see which of them have data...
Did you mean one of these, or was it a serious statement?
Serious.
At least for some simple FTP client cases I believe it is possible for
the app to know what connection to read from when.
Agreed. I am not aware of any requirement for either end to do anything to
the control connection while a transfer is in progress, and while a
transfer is not in progress, if there is a data connection, there is
nothing that needs to be done to it.
tom
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LEDERHOSEN IS NOT EDIBLE
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