Spooler Components and IHV Development Opportunities

The components of the Windows NT spooler are outlined in the following table.

Component/Description

Default Executable

IHV Development Requirement s

Spooler Server Process: entrance to the spooler subsystem for both local and remote print requests.

spoolss.exe

None: the Microsoft-provided service cannot be replaced.

Print Request Router (PRR): routes a print request’s data stream to the local or network print provider.

spoolss.dll

None: the Microsoft-provided PRR cannot be replaced.

Local Print Provider: responsible for the local playback of spooled print jobs. This includes putting print jobs into spool files, managing despooling, and performing administrative tasks such as print queue management.

localspl.dll

None: the Microsoft-provided local print provider cannot be replaced.

Network Print Provider: responsible for translating print requests from Win32 printing function calls to a vendor-specific form that can be used by the network.

win32spl.dll

Printer IHVs typically do not need to develop a network print provider.
Network IHVs must develop one.

Print Processors: perform despooling.

winprint.dll

Winprint handles three spool file formats: raw, EMF, and text; it is the default print processor. Print processors and printer drivers work together, so printer vendors may wish to develop another print processor if the vendor supports a different spool file format.

Port Monitors: Responsible for communication between spooler and printing device. Typically communicates with base I/O drivers (i.e. serial and parallel drivers) for device I/O, but may also call different interfaces, such as Windows Sockets, SCSI, etc.

localmon.dll

Printers that use parallel or serial ports can use localmon.dll. IHVs with printers that connect to other types of ports, such as SCSI or Ethernet LAN cards) need to develop a port monitor. See Print Monitors for more information.

Language Monitors: allow the spooler to configure and monitor the status of a bidirectional printer.

none

If the printer manufacturer’s device is bidirectional, vendors can develop a language monitor for it. See Print Monitors for more information.

Component/Description	Default Executable	IHV Development Requirement s
Spooler Server Process: entrance to the spooler subsystem for both local and remote print requests.	spoolss.exe	None: the Microsoft-provided service cannot be replaced.
Print Request Router (PRR): routes a print request’s data stream to the local or network print provider.	spoolss.dll	None: the Microsoft-provided PRR cannot be replaced.
Local Print Provider: responsible for the local playback of spooled print jobs. This includes putting print jobs into spool files, managing despooling, and performing administrative tasks such as print queue management.	localspl.dll	None: the Microsoft-provided local print provider cannot be replaced.
Network Print Provider: responsible for translating print requests from Win32 printing function calls to a vendor-specific form that can be used by the network.	win32spl.dll	Printer IHVs typically do not need to develop a network print provider. Network IHVs must develop one.
Print Processors: perform despooling.	winprint.dll	Winprint handles three spool file formats: raw, EMF, and text; it is the default print processor. Print processors and printer drivers work together, so printer vendors may wish to develop another print processor if the vendor supports a different spool file format.
Port Monitors: Responsible for communication between spooler and printing device. Typically communicates with base I/O drivers (i.e. serial and parallel drivers) for device I/O, but may also call different interfaces, such as Windows Sockets, SCSI, etc.	localmon.dll	Printers that use parallel or serial ports can use localmon.dll. IHVs with printers that connect to other types of ports, such as SCSI or Ethernet LAN cards) need to develop a port monitor. See Print Monitors for more information.
Language Monitors: allow the spooler to configure and monitor the status of a bidirectional printer.	none	If the printer manufacturer’s device is bidirectional, vendors can develop a language monitor for it. See Print Monitors for more information.