FTP and IPv6 (RFC-2428)

Hi all,
I have the FTP server in my signature to wich I'd want to add IPv6
support.
I'm having trouble with understanding how to implement the EPSV
command described in RFC-2428: http://www.ietf.org/rfc/rfc2428.txt

RFC-2428 says:



> When the EPSV command is issued with no argument, the server will
> choose the network protocol for the data connection based on the
> protocol used for the control connection.
> However, in the case of proxy FTP, this protocol might not be appropriate
> for communication between the two servers. Therefore, the client needs to
> be able to request a specific protocol.
> [...]
> The client can send an EPSV command requesting the use of a specific
> network protocol, as follows:

> EPSV<space><net-prt>


> If the requested protocol is supported by the server, it SHOULD use
> the protocol. If not, the server MUST return the 522 error messages
> as outlined in section 2.



What does this mean? That, for example, a client connected on the
command channel through IPv4 can ask the server to open a passive
data
channel using IPv6?
If so how could I be able to open an IPv6 socket without knowing to
which address I have to bind it on?
I guess there's something I'm missing here.

Thanks in advance.


--- Giampaolo
http://code.google.com/p/pyftpdlib