Open /opt/local/etc/macports/archive_sites.conf as root.
Add the following two lines:
name local_archives
urls http://jog.id.packages.macports.org/macports/packages/
You can also disable all the official archive mirrors by doing like this:
name macports_archives
name local_archives
urls http://jog.id.packages.macports.org/macports/packages/