ftp://ftp.xemacs.org doesn't do "PASV" correctly -- makes it tricky to update XEmacs packages from behind a NAT

[Samuel Bronson]

I can't access ftp://ftp.xemacs.org from behind a NAT. It's not just
an EFS problem, either -- I tried it with Chrome, too, and that didn't
work either.

It also isn't a problem with my connection/NAT: I can access
ftp://ftp.gnu.org just fine with EFS and with Chrome.

It seems to understand the PASV command well enough, but the data
connection itself doesn't seem to go through, so I suspect that the
ftp server and firewall configurations have gotten out of sync, so
that PASV returns connection parameters containing ports that get
filtered. Wireshark didn't really show much except the connections
seeming to time out. (My cable modem drops all ICMP packets -- it told
me so! -- so I can't say whether there were any or not.)

(Strangely, sometimes EFS seems to get a whole lot of NULs in the FTP
process buffer, but I don't know where they come from.)

All of this wouldn't be much of a problem -- I could still access the
files by http -- except that package installation doesn't support
that.

It seems that ftp://ftp.ca.xemacs.org is working today, though.