Dell 1600n Network scanning and printing

We recently purchased a Dell 1600n printer for use in a small outlying office.  The office is connected to a data centre using VPN on the firewalls.  We are predominantlly using citrix terminal services for the users.  It was easy enough to set up the printer using network setup to a local laptop within the office subnet (providing one turned off windows firewall) but the problems started when trying to set up the system from the data centre.

When trying to install from the data centre, the full install would not work.  I could ping the printer with no problems, but it could not be found by the software therefore it was impossible to continue the install routine. Can anyone advise why if I can ping the printer (and use the web interface) that this should be so?  What are the ports that might be being blocked on the firewall that require to be open to find the printer across the WAN?

The printer could be installed easily as a printer by adding an appropriate standard TCP/IP port on the print server in the data centre, so printing was not a problem.

It was possible to set up scanning by running just the NetScan install on the Citrix Server, and the scanner could be identified and would scan intermittently.  The settings were adjusted to place the output in a suitable folder and not open the file for viewing.  However because the utility now appears in the taskbar of every citrix user, the system appears to become confused and cannot differentiate the sessions on the citrix server.

It is unfortunate that although the system uses TWAIN it is a push to the client.  Normally Citrix PS4 can use TWAIN driver installed locally on a client to obtain information, but the 1600n uses WIA drivers in this mode.

Can anyone shed any more light on this issue of how to install the 1600n across a WAN, and any terminal services considerations that might be required for use in this environment.

thanks

David Denholm