Progress bar on FTP download

[agraham]

Originally Posted by dennishea

How does explorer display the size of the file to be downloaded and the amount thats downloaded so far? Thats what you are talking about, right?

The answer to this is bit more complicated than you might think. The following is simplified, and perhaps not entirely correct, but hopefully it provides some sort of explanation.

Many .NET/Operating System functions are available in both synchronous and asynchronous form. B4PPC offers only the synchronous forms for simplicity.

Synchronous operations basically block the caller until they either succeed or fail, so they need no further management by the caller. Thus they are simple to use and that is why B4PPC restricts itself to them.

Asynchronous operations in comparison need ongoing management by the caller. Typically they involve calling a function to get things going which launches a separate thread and registers a "callback function" or event that the thread calls to handle the completion of the operation. The caller is then free to do other things and when the completion event occurs must call a finalise function to get the data from the operation thread and tidy things up.

Crucially however, in order to monitor progress the, in this case FTP, process must be written with the ability to report on its' progress, via another callback, if used asynchronously. The .NET FTP functions do not do this. Explorer is probably using either its' own FTP process built on top of the OS TCP/IP stack, or is using a lower level OS facility that does provide progress monitoring.

[dzt]

Before posting for the first time in this topic I had made a successful test (desktop only)

[RandomCoder]

It's just an idea and not very reliable but....
If you know the size of the file to be downloaded and have a rough idea of the rate at which it transfers then you could just make a 'best guess' and use a timer to set the update of the progress bar.

Regards,
RandomCoder

[willisgt]

Okay - first approach was to download the file in the main code and use the thread to update the progress bar. Didn't work for reasons explained previously in this thread.

So i tried turning it around - if only the main thread can update the GUI, then use the main code to update the progress bar, and use the thread to download the file.

Bingo!

[agraham]

use the main code to update the progress bar, and use the thread to download the file

Yes, I think this is what dzt intially suggested and what we thought you were trying to do. It never even crossed my mind that you were trying the other way round

Originally Posted by dzt

You can run ftp commands in a seperate thread using Thread object. In your main thread add a timer and check the filesize of the file you are downloading

[dennishea]

Thanks Agraham for the reply. I think I have a grasp of what your saying.

dennishea

[willisgt]

Looking back, that's exactly what Dimitris suggested.

Could've saved myself a lot of grief if I'd read it a little more closely (and fully grasped the problem at the outset).

Guess that's one of those little gaps between concept and implementation...