[thelist] ActiveX FTP Object

Steve Lewis slewis at macrovista.net
Tue Aug 13 18:17:01 CDT 2002


Joshua Olson wrote:
> Does anybody know of an FTP object that will allow for multiple GETs to be
> performed in realtime with a single connection?  I've looked at some of the
> Freeware utilities that get files one at a time, but they incur an overhead
> when the connection is created.

By design, you cannot perform multiple simultaneous GETs by FTP.  The
FTP protocol does not support this behavior.  Multiple concurrent GETS
require one connection each.

BTW, the behavior known as 'leeching' is generally not appreciated by
hosts, which is why many modern FTP servers will limit anonymous users
to a small # of concurrent connections (sometimes only 1!) and/or
throttle bandwidth of each connection... which is probably why you find
yourself in this dilemna.  I will also point out that the way TCP/IP is
designed you are not supposed to be able to get 5 files faster by doing
them all at once than you would by downloading them in serial (one at a
time).

With that understanding, you could create a new protocol (it's not that
hard) that stands on the shoulders of giants ... and create a toy client
and server app easily in Java as proof of concept ... which would accept
a list of files to GET, dump them into a JAR/ZIP archive, transfer the
archive on one TCP connection, and unJAR/ZIP them on the client end, in
realtime.  The only benefit you would have over an automated/scripted
traditional FTP is when you were working with large numbers of small
files where the handshaking and setup for each file becomes prohibitive
(when deploying a large static website for example with lots and lots of
relatively small-- < 20k --text files).

Of course there are shortcomings you would need to deal with. Such as,
if the archive was not completely xfered or errors were introduced you
could recover NONE of the component files because the archive would be
invalid (an artifact of how ZIP and most every file compression/archive
algorithm works).  This is generally how we xfered fidomail (email)
messages and echomail (newsgroups) back in my BBS days.




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