FTP and Error Correction

[gjrhine]

Is there some kind of error checking going on with FTP? Can I assume if the file sizes are the same everything is OK. Also, I notice there is no such thing as Pause. If I abort then restart is there any greater risk of the destination file having a problem? Thanks. Purchased the program and liking it so far.

[bigstar]

The basic FTP protocol does not provide error checking, there are some extensions to the FTP protocol that offer MD5/SHA1 hashing of a file to compare the local vs remote but in many cases you'll find that the ftp server software doesn't support it. Currently FlashFXP doesn't support them either but as more ftp servers support them we'll being adding support on our end as well.

Aborting a file transfer is an iffy subject because of the way works, by design its rather poorly implemented and it varies a lot between ftp server software.

Aborting a download file transfer can result in corruption in some cases, FlashFXP has a rollback option that will truncate the file by a few KB and effectively remove any possible corruption before resuming the transfer.

Normally you don't see much corruption when aborting an upload but there's always a possibility.

[gjrhine]

Aborting a download file transfer can result in corruption in some cases, FlashFXP has a rollback option that will truncate the file by a few KB and effectively remove any possible corruption before resuming the transfer.

Normally you don't see much corruption when aborting an upload but there's always a possibility.

Is the rollback option "Use APPE to resume uploads"? I would like to do everything I can to increase the chances for a good upload of a 8 gig video file.

[DayCuts]

Hmm, i thought i recalled a setting for the amount of rollback, but i guess im wrong. So i guess the feature is automatic? or im blind heh.

[MxxCon]

there is no 'rollback' option for uploads, only downloads.
you might want to use sftp protocol since by its nature of encryption, it ensures that every delivered packet is intact.
your destination server must also support such large file sizes. destination ftp/ssh server might not support it.
your best bet would be to cut up this file into smaller chunks, upload them and then merge it on the destination computer.

[gjrhine]

Can sftp be set in FlashFXP? I do not see it anywhere. My destination is the Popcorn Hour media player through a wireless bridge adapter. I do not see reports of corrupt files on the Popcorn Hour forums but I am just checking on how to ensure a good success rate.

[MxxCon]

ah, originally you didn't say where you were going to be uploading that file.
popcorn pour media player does not support ssh/sftp.
since it's a local connection, file transfer will go pretty fast so if some corruption will happen, it won't be a problem to reupload.

[gjrhine]

But I may not know of corruption until after, say, 2 hours of watching video, right?

[bigstar]

for media files sftp probably isn't the best solution, transfer speeds are much slower than ftp and it would take ages for an 8gb file. also the destination host much support sftp and more than likely it doesn't.

sftp is available in the latest beta release of FlashFXP.

[gjrhine]

Thanks. One last question. Is it possible I would not know of ftp corruption until well into watching a video file?

[MxxCon]

is it "possible"? sure. but pretty unlikely.

[gjrhine]

Thanks. No problems in about 10 files so far. :)

[DayCuts]

randomly corrupted bytes in an uploaded video file are almost always 'noticable', generally in the form or a few frames of a single frame with a few miscolored pixels or a slitch sound beep/click. however it is highly unlikely that such a minor glitch will be bothersom. this is generally the extent in which corrupted packets in video will manifest, but in rare cases it can cause major audio glitches resulting in offsets/desync or loss of audio from that point on or constant blocking/broken pixels throughout the video and even video not playing and crashing the player software. such cases are very uncommon and if you were to experience something like this chances are the transfer would not have succeded anyway as the same cause would likely drop ack's and make it fail.