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Re: Theads and FTP

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On Mon, 5 Dec 2011, Arne Vajhøj wrote:

> On 12/5/2011 9:58 AM, Andreas Leitgeb wrote:
>> Arne Vajhøj<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

-- 
LEDERHOSEN IS NOT EDIBLE

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Theads and FTP Roedy Green <see_website@mindprod.com.invalid> - 2011-12-03 20:31 -0800
  Re: Theads and FTP Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2011-12-04 13:14 -0800
    Re: Theads and FTP Arne Vajhøj <arne@vajhoej.dk> - 2011-12-04 22:06 -0500
      Re: Theads and FTP Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-12-05 14:58 +0000
        Re: Theads and FTP Arne Vajhøj <arne@vajhoej.dk> - 2011-12-05 22:01 -0500
          Re: Theads and FTP Tom Anderson <twic@urchin.earth.li> - 2011-12-06 21:07 +0000
    Re: Theads and FTP Roedy Green <see_website@mindprod.com.invalid> - 2011-12-05 05:33 -0800
      Re: Theads and FTP Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2011-12-05 09:29 -0800
      Re: Theads and FTP Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-12-05 12:29 -0600
        Re: Theads and FTP Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-12-06 11:28 -0600
      Re: Theads and FTP Arne Vajhøj <arne@vajhoej.dk> - 2011-12-05 22:00 -0500
      Re: Theads and FTP Tom Anderson <twic@urchin.earth.li> - 2011-12-06 22:16 +0000
  Re: Theads and FTP Arne Vajhøj <arne@vajhoej.dk> - 2011-12-04 22:04 -0500

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