Our assumption is that the print spooler service is not working correctly and this has also been confirmed in our tests. The problem is created by Windows related processes. This phenomenon is known as ‘Ghost Printer’. printers are shown in Devices & Printers as “unknown device”.printers cannot be deleted from old printer view but from Devices & Printers.default printer is shown but not really existing when you want to select it from the application when printing,.default printer cannot be set (any error),.multiple printers having the same name (network printer shares as well as local printers),.“not available” in ThinPrint Self Service.These all have in common, that there are inconsistent printer object lists in “Devices and Printers”, “Printers” and API-“enumprinters”. These manual printer queues from the previous session now are automatically announced to the server by MSTSCAX.DLL (client RDPDR.LIB) and can now be viewed as automatic printer queues.In a terminal server 2012R environment using ThinPrint with network shared printers a number of problems occur which are most likely connected to the same issue. These printers were persisted by the client in the registry (see Details of Queue Configuration Changes). In addition to the printers that were automatically detected, the client also announces printers that were manually created in a previous session by the user or administrator. The client sends data for each enumerated printer, including printer name, printer type (for example, network or local), driver name, and any configuration data, such as paper orientation (portrait or landscape) or number of pages per sheet, that was previously saved by the client in the registry. The printers automatically detected via the EnumPrinters() API are always called automatic printer queues. In RDP 5.0, only printers connected locally to the client machine via COM, Serial, or USB ports are redirected in Terminal Server sessions.

Printers are enumerated using the EnumPrinters() API. The client-side RDPDR subcomponent within MSTSCAX.DLL enumerates printers on the client and announces them to the server.

With regard to printing, it is a TS client-side component that implements the RDP Virtual Channel for redirected printing. MSTSCAX.DLL is the Terminal Services Client ActiveX Control.

Windows api enumprintersw