#632 ftp mode active/passive performance

[Christophe De Clercq]

When I connect to a server though a firewall using
the unix ftp command both active an passive mode work
fine (tested with the dir command).

When using active mode (the default) via tcllib(v 1.7)
ftp it takes
in my case more than 40seconds before I get a response
with ftp::NList. When setting to passive mode it works fine
without the delay.

Why the difference ?