FTP and local file compare
lazarus / 38-Networking and Web Programming

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cybersmyth · 2011-03-22 11:29

This might be a really dumb question, but I just want to make sure...

I'm working on an FTP client using lNet and want to be sure uploads
and downloads complete fully. My thought is to do a FTP listing and
compare the file size of the local file to the remote file to verify
it uploaded fully.

Is the workable? Are there any situations where a file might have
uploaded properly but the directory listing would show a different
size than the local file?

Thanks!
-Joe

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joseme · 2011-03-22 17:02

Your proposal is workable, but if you want to cath file corruption I
think you can use Ciclic Redundance Check, putting a small text file
with the CRC of files to download, and later calculating the CRC for
the received files and comparing.

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TurboRascal · 2011-03-22 20:18

It is possible that there is some difference in filesize counting, but
I believe if both are got in bytes it should be ok. CRC is not a bad
idea for file upload, although there is no similar possibility to
check downloads. And there is always a risk of getting a corrupted
download, even when bytesizes are identical (bit flipping errors etc.)
and there is no way to check for that.