From: DeskNow Knowledge Base
http://www.desknow.com/kb/

DeskNow is using TCP version 6 (ipv6) - I want it to listen only on version 4 sockets (ipv4).
http://www.desknow.com/kb/idx/12/095/article/

on OSes where ipv6 is enabled (ex. modern Linux Debian), Java by default will use ipv6 for networking.

To force it to use ipv4:

Edit /etc/desknow.conf and set this line:

JAVA_OPTS="-Xms32m -Xmx256m -Djava.net.preferIPv4Stack=true"

Then restart DeskNow.