In normal mode the server opens a connection to the FTP client; in PASV
mode the client instead opens a connection to the server, so it'll work
through a firewall.
On Tue, Jan 5, 2021 at 2:09 PM Joachim Durchholz
Am 05.01.21 um 16:54 schrieb Kees Bleijenberg:
Unfortunately is ‘working in passive mode’ not so easy (at least not to me). After login I send the ‘pasv’ command and I get back a IP address and a port (I assume). Do I have to create a new connection with a handle to this new port for the stor command?
Yes.
I don’t know how to do that in network.ftp.client.
If network.ftp.client does not support that out of the box, you'll either have to find another library or add PASV support to it.
My knowledge of the FTP protocol is pretty rusty, but I believe you the model after PASV is that you continue using normal commands but the data transfers happen over the other connection. I'd watch out for how the protocol marks the beginning and end of a data stream (it's not a single connection anymore so you lose the sequencing guarantees of TCP packets; I'd assume they either send a special packet on the data connection, or they transmit the file sizes via the normal channel).
However, I can't avoid wondering why anybody would want to use the FTP protocol at all. It's so unsafe, so bottleneck-endangered, the only reason to do that would be interfacing with existing FTP servers, and even these are being phased out in favor of HTTPS, with POST for uploads. (I'm not questioning the validity of your use case, just wondering how such a use case can come up in today's world.)
Regards, Jo _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.
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