[Zope] Re: FTP from NAT: Zope or FTP problem...

[Bob Finch]

>>>>> "Chris" == Chris Withers <chrisw@nipltd.com> writes:

    Chris> Bob Finch wrote:
    >> 
    >> Try configuring your FTP client to use passive mode (PASV).

    Chris> Now is this because Zope is doing something silyl or
    Chris> because FTP behind NAT is like SSH, and must be passive
    Chris> regardless of the FTP server you're using?

This is an issue with FTP and NAT in general.  PASV also helps if the
client has a firewall or packet filter that denies incoming TCP
connections.

When transferring a file in the default (active) mode, the FTP server
opens a TCP connection back to the client.  Some NAT implementations
aren't smart enough to be able to route this incoming connection to
the correct internal host.

Passive FTP avoids this problem by doing outgoing connections from the
client for the data transfer.  During a file transfer, the server
instead waits for an incoming connection from the client.  No more
incoming TCP connections and NAT is happy :-)

-- Bob