XenApp 6.0: Printers Fail to Autocreate on a Mac

I got a call from one of our users that has a Mac at home and connects to our Citrix XenApp farm through our Access Gateway.  Apparently, everything was working fine, except that the printers locally attached to his Mac would not auto-create in his Citrix session.

While I enjoy using my Macbook at home, we have no Apple gear here in our office, so I was unable to do any tests in our lab environment.  That's when I decided to call on the power of Google for help, and stumbled across the following Citrix article: Printers Defined on a Mac Client Fail to Auto-Create when Connecting to XenApp 5.0 on Windows 2008

Basically, the issue was that a printer driver (the HP Color Laserjet 4500 PS for XenApp 5, or the HP Color Laser Jet 2800 Series PS for XenApp 6) was no longer installed on our XenApp servers.  Early on, before we learned about the pains of printing in Citrix, we freely installed drivers for printers.  After finding out that was a very bad idea, I went on a driver purging spree, only allowing battle-tested drivers that were absolutely necessary to be installed on our farm.  I must have deleted the required driver in this process, as it is apparently installed by XenApp automatically.

For those curious, the reason why you need these HP drivers in the first place is because, for the time being, the driver that Citrix uses for their Universal Print Driver is not compatible with Macs.  So -- if you find that your Mac printers are not auto-creating, double check to make sure the required driver is installed!

Random Empty Print Jobs Sent to Network Printers

I recently came across an odd problem having to do with empty print jobs being sent to printers across our network.  Since our printers are all configured to first print a cover sheet with the user's username before each job, this would result in dozens of coversheets being printed on various printers throughout our company.  After a closer inspection, the jobs being spooled were all named "Remote Desktop Redirected Printer Doc" -- so I knew that Remote Desktop had something to do with it at least.

At some point in the troubleshooting process I found that I could recreate the problem at will (which is gold in the technical troubleshooting world).  All I had to do was start a remote desktop session from a computer with network printers installed, to an XP computer on our network.  I also had to choose the option to redirect local printers to the remote session for it to occur as well.  Whichever network printers were installed on the local machine, and were redirected to the remote session, would receive a random amount of these empty print jobs.

After scouring the internet for awhile, and involving Microsoft support, I discovered that our problem was related to a little 3rd party application called Scan2PC.exe -- which was installed with some drivers to a Dell multifunction printer that all of our executives have.  So, if we started a remote desktop session to any XP computer that had this application installed, the problem happened.  As soon as I removed the Dell drivers, the problem went away.  Since our executives aren't planning getting rid of their brand new multifunction devices anytime soon, our current work around is to uncheck the box in the RDP session to redirect local printers to the remote session.

It's crazy how such a small thing can cause so many weird things to happen!

"The specified port is unknown" When Adding a Network Printer

We currently have a Windows 2008 x64 Server with print services installed and we are sharing several network printers through that server. Every time a user logs in, a vbs script is run that maps certain printers for them depending on which groups they belong to in Active Directory. All was well and good until randomly we started getting the error message "The specified port is unknown" on one of our servers when trying to add the printers. So, instead of mapping the specified printers, the logon script failed leaving the user printerless. I then went on to test adding the printer manually through the control panel, and to my surprise, I got the exact same error. What gives?

I tried several things on the server hosting the printer, but it made absolutely no difference whatsoever. Finally, I thought, maybe if I just restart the Print Spooler service on the server the user was logging into. As soon as I did that, everything worked again! So, I'm not exactly sure what caused the problem to occur in the first place, but I'm glad that I know how to fix it now.

Bonus: We were also having issues with the wrong username/job owner showing up on the printer separator sheets. Instead of printing the username of the person who printed, it would print the username of the last Domain Admin to print something. We searched Google near and far and came back with nothing. After running out of ideas, we pinged Microsoft support on the issue to discover that this is a known problem with Server 2008 and Vista SP1 and there's actually a hotfix available for it: http://support.microsoft.com/kb/958741 I hope that someone finds this useful, since I had such a hard time finding the solution.