Copy and paste the following line into a text file. See also this faq for information on how to use the configuration file.

www.netopti.net

# This is configuration file for
# http://www.netopti.net/
# dynamic DNS service provider
#
# No change is needed in this file
#
[default]
withpass=0
host=update.netopti.net
port=80
path=/dns/dnsupdate.php

[requests]
hostname=%HOST%
username=%USER%
password=%PASS%
myip=%IP%

[result]
multilines=0
success=1000
warning=1001