Many, many thanks. This worked for me.
My HP 2100TN is connected to a router and pinging the JetDirect ip address didn't work at first. After many tries and variations under "Print & Scan" sys prefs, the ping did work with the JetDirect ip address and I finished connecting by following your helpful instructions and links.
The HP 2100TN now prints from OSX 10.8.5 on a "late 2012" 27-inch iMac. The HP 2100TN printer drivers were copied to the sys printer folder from a previous computer running OSX 10.5.8 and which always printed sucessfully through this same router to the 2100TN and still does.
An even worse problem was trying to log into Apple Support Communities with the "username" endless runaround. I finally got to a "Find my Apple ID" link and discovered I had an old Apple ID which I didn't know still existed. I changed the password on that ID and then logged into ASC using the old ID. The login took me straight into the forum and displayed my old and long-forgotten ASC username for that ID. Why that worked, who knows?