Hi.
I'm the author of
drftpd, which needs a minor protocol extension to be able to use of PASV.
I've written a comprehensive specification on the command here, i hope you find all your questions answered in the spec
http://drftpd.mog.se/wiki.phtml?title=Distributed_PASV
Currently drftpd has very few users, but i'm in the process of setting up a larget cluster. Of course, PASV isn't required but is certainly nice for the FlashFXP users behind NAT/FXPing to another PASV-only site.
The specification is intended for easy implementation and the only thing needed is to send a "PRET <transfer-command>" command before PASV. Any response from the command can safely be ignored. You might want to disable sending PRET if the response code is 202, 500 or 502 though.
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mog
DrFTPD author
Distributed PASV: PASV with PRE Transfer Command
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