Apple DMG files over FTP are getting corrupted why?

Question

I am trying to FTP some apple DMG files, if we do it by hand through Safari or IE it ends up at the destination just fine and uncorrupted. However, if I use a freeware FTP client that we had been using with great success for zip's and exe's or if I use a Powershell script I finished off (adapted from another stackover flow's question's answer) then I lose about a 1/2 Mb on a 10.5 Mb file and the dmg is corrupted. Does anyone have anyclues what could be going wrong? Things I could do to prevent it? So far all I have tried is gzipping the dmg before sending and that accomplished nothing. Again, anything but a dmg gets transmitted just fine.

FYI I am using binary mode transfers, so that is not it..thx though

Answer 1

Seems like your client treats dmg file as text file. set Binary transfer mode in your ftp client and it will ftp it as is.

I always thought that ascii transfer mode in ftp is just plain stupid. It causes more trouble then it is worth.

Answer 2

Are you sure everything except a DMG gets transferred correctly? It sounds like a problem with the transfer encoding. FTP supports both binary and ASCII transfer types, mainly due to historical baggage. In ye old days, when bandwidth was scarer, leaving off the high bit (which ASCII doesn't use) was a good time saver. However, if you have any bytes with the bit set, ASCII transfer mode will lose them - hence "binary" mode, which truncates nothing.

Typically, the command to switch transfer modes is "bin" or "ascii".

Answer 3

Just so everyone knows. It must have been the client I was using had the exact same issue as my PowerShell script. I was using StreamReader to get the bytes for transfer and it was assuming an encoding which was not correct. I switched to a BinaryReader which does not, and it now works.