The USB device is not a disk drive, but a teleprompter. Data is sent when
requested from the device. So single bytes from the device result in large
amounts of data being sent from the PC to the USB device. All this works. It
is only when the FTP is getting data that it can go pear shaped. While the
FTP data is being processed, the USB is continually monitored and FTP
processing is interrupted to service the USB. All this works on my system
and I just need some ideas as to what can cause this at the customer site.
>From what you say, you are ruling out the FTP client itself. I shall try and
get some ICS logging files to compare.


-----Original Message-----
From: [] On
Behalf Of Angus Robertson - Magenta Systems Ltd
Sent: 27 January 2011 14:31
Subject: Re: [twsocket] Using the FTP Client

> somehow the application can at times no longer get data from the USB 
> quick enough.

Disk I/O in Windows can be blocking, you normally only see it with bad disk
sectors when the event log shows lots of errors in red when it times out
waiting for a response from the drive.  If this is the sort of error the USB
memory key is causing, Windows will be upset. 

> Is it possible that the FTP transactions can, for whatever network >
reasons> hog the CPU resources so that my application cannot get
> access to the USB data?

No, FTP uses very little CPU.  I was testing the new bandwidth throttling a
few months ago, with both ICS FTP client and server, and using one thread
per FTP client I was successfully running 250 simultaneous FTP sessions
(using my TMagFtp component), that is proper sessions each indexing files
and downloading multiple real files at the same time.  I even had 100
session to my public FTP server over the internet. 

Durations did increase as number of sessions went up, but never stopped, and
that was on my old Core2 PC with 32-bit Windows and little memory, my newer
PC is much more beefy and it's all 64-bit now, but not had time to test


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