CUPS Implementation of IPP


CUPS-IPP-1.1
Easy Software Products
Copyright 1997-2003 All Rights Reserved

Table of Contents



1 Scope 2 References 3 Overview 4 Operations 5 Attributes A Glossary

1 Scope

1.1 Identification

This document provides an overview of the Internet Printing Protocol ("IPP") version 1.1 as implemented in the Common UNIX Printing System ("CUPS") version 1.1.

1.2 System Overview

CUPS provides a portable printing layer for UNIX®-based operating systems. It has been developed by Easy Software Products to promote a standard printing solution for all UNIX vendors and users. CUPS provides the System V and Berkeley command-line interfaces.

CUPS uses the Internet Printing Protocol ("IPP") as the basis for managing print jobs and queues. The Line Printer Daemon ("LPD") Server Message Block ("SMB"), and AppSocket (a.k.a. JetDirect) protocols are also supported with reduced functionality. CUPS adds network printer browsing and PostScript Printer Description ("PPD") based printing options to support real-world printing under UNIX.

CUPS includes an image file RIP that supports printing of image files to non-PostScript printers. A customized version of GNU Ghostscript 7.05 for CUPS called ESP Ghostscript is available separately to support printing of PostScript files within the CUPS driver framework. Sample drivers for Dymo, EPSON, HP, and OKIDATA printers are included that use these filters.

Drivers for thousands of printers are provided with our ESP Print Pro software, available at:

    http://www.easysw.com/printpro/

CUPS is licensed under the GNU General Public License and GNU Library General Public License. Please contact Easy Software Products for commercial support and "binary distribution" rights.

1.3 Document Overview

This document is organized into the following sections:

2 References

2.1 CUPS Documentation

The following CUPS documentation is referenced by this document:

2.2 Other Documents

The following non-CUPS documents are referenced by this document:

3 Overview

CUPS 1.1 implements IPP/1.1 and the operations and attributes defined in the "IPP: Job and Printer Set Operations", "IPP/1.1: Output-bin Attribute Extension", and "IPP/1.1: finishings 'fold',' trim', and 'bale' attribute values extension" specifications.

CUPS also provides 13 new operations and many new attributes to support multiple IPP printers and printer classes on a single host.

3.1 IPP URIs

CUPS supports both the "http" and "ipp" methods. The following resource names are used:

method://hostname:port/
Can be used for all "get" operations.
method://hostname:port/admin
Used for all administrative operations.
method://hostname:port/classes/name
Specifies a printer class.
method://hostname:port/jobs/id
Specifies a job.
method://hostname:port/printers/name
Specifies a printer.

So a typical printer URI would be "ipp://foo.bar.com/printers/LaserJet".

In addition, the CUPS server also supports normal browser access to "method://hostname:port/admin/", "method://hostname:port/classes/", "method://hostname:port/jobs/", and "method://hostname:port/printers/" to view and manage resources on the server dynamically.

3.2 CUPS IPP Operations

CUPS provides 13 extension operations in addition to most of the standard IPP and registered extension operations:

Operation NameCUPS CodeBrief Description
Print-Job1.0 0x0002Print a file.
Validate-Job1.0 0x0004Validate job attributes.
Create-Job1.1 0x0005Create a print job.
Send-Document1.1 0x0006Send a file for a print job.
Cancel-Job1.0 0x0008Cancel a print job.
Get-Job-Attributes1.0 0x0009Get job attributes.
Get-Jobs1.0 0x000AGet all jobs.
Get-Printer-Attributes1.00x000BGet printer attributes.
Hold-Job1.1 0x000CHold a job for printing.
Release-Job1.1 0x000DRelease a job for printing.
Pause-Printer1.0 0x0010Pause printing on a printer.
Resume-Printer1.0 0x0011Resume printing on a printer.
Purge-Jobs1.0 0x0012Purge all jobs.
Set-Job-Attributes1.1 0x0014Set attributes for a pending or held job.
CUPS-Get-Default1.0 0x4001Get the default destination.
CUPS-Get-Printers1.0 0x4002Get all of the available printers.
CUPS-Add-Modify-Printer1.00x4003Add or modify a printer.
CUPS-Delete-Printer1.00x4004Delete a printer.
CUPS-Get-Classes1.0 0x4005Get all of the available printer classes.
CUPS-Add-Modify-Class1.00x4006Add or modify a printer class.
CUPS-Delete-Class1.0 0x4007Delete a printer class.
CUPS-Accept-Jobs1.0 0x4008Accept jobs on a printer or printer class.
CUPS-Reject-Jobs1.0 0x4009Reject jobs on a printer or printer class.
CUPS-Set-Default1.0 0x400ASet the default destination.
CUPS-Get-Devices1.1 0x400BGet all of the available devices.
CUPS-Get-PPDs1.1 0x400CGet all of the available PPDs.
CUPS-Move-Job1.1 0x400DMove a job to a different printer.

4 Operations

The following sections describe the operations supported by CUPS. In the interest of brevity, operations which use only the standard IPP attributes are not described.

4.1 Print-Job Operation

The Print-Job operation (0x0002) prints a file.

4.1.1 Print-Job Request

The following groups of attributes are supplied as part of the Print-Job request:

Group 1: Operation Attributes

Group 2: Job Template Attributes

The Print-Job request is followed by a file to be printed.

4.1.2 Print-Job Response

The following groups of attributes are send as part of the Print-Job Response:

Group 1: Operation Attributes

Group 2: Job Attributes

4.2 Create-Job Operation

The Create-Job operation (0x0005) creates a new, empty print job.

4.2.1 Create-Job Request

The following groups of attributes are supplied as part of the Create-Job request:

Group 1: Operation Attributes

Group 2: Job Template Attributes

4.2.2 Create-Job Response

The following groups of attributes are send as part of the Create-Job Response:

Group 1: Operation Attributes

Group 2: Job Attributes

4.3 Set-Job-Attributes Operation

The Set-Job-Attributes operation (0x0014) changes the attributes of an active (not completed) job.

4.3.1 Set-Job-Attributes Request

The following groups of attributes are supplied as part of the Set-Job-Attributes request:

Group 1: Operation Attributes

Group 2: Job Template Attributes

4.3.2 Set-Job-Attributes Response

The following groups of attributes are send as part of the Set-Job-Attributes Response:

Group 1: Operation Attributes

4.4 CUPS-Get-Default Operation

The CUPS-Get-Default operation (0x4001) returns the default printer URI and attributes.

4.4.1 CUPS-Get-Default Request

The following groups of attributes are supplied as part of the CUPS-Get-Default request:

Group 1: Operation Attributes

4.4.2 CUPS-Get-Default Response

The following groups of attributes are send as part of the CUPS-Get-Default Response:

Group 1: Operation Attributes

Group 2: Printer Object Attributes

4.5 CUPS-Get-Printers Operation

The CUPS-Get-Printers operation (0x4002) returns the printer attributes for every printer known to the system. This may include printers that are not served directly by the server.

4.5.1 CUPS-Get-Printers Request

The following groups of attributes are supplied as part of the CUPS-Get-Printers request:

Group 1: Operation Attributes

4.5.2 CUPS-Get-Printers Response

The following groups of attributes are send as part of the CUPS-Get-Printers Response:

Group 1: Operation Attributes

Group 2: Printer Object Attributes

4.6 CUPS-Add-Modify-Printer Operation

The CUPS-Add-Modify-Printer operation (0x4003) adds a new printer or modifies an existing printer on the system.

Note:

This operation requires administrative priviledges and must be POSTed to "/admin/". POSTs to other paths will result in a client-error-not-authorized (IPP_NOT_AUTHORIZED) error.

4.6.1 CUPS-Add-Modify-Printer Request

The following groups of attributes are supplied as part of the CUPS-Add-Modify-Printer request:

Group 1: Operation Attributes

Group 2: Printer Object Attributes

The CUPS-Add-Modify-Printer request can optionally be followed by a PPD file or System V interface script to be used for the printer. The "ppd-name" attribute overrides any file that is attached to the end of the request with a local CUPS PPD file.

4.6.2 CUPS-Add-Modify-Printer Response

The following groups of attributes are send as part of the CUPS-Add-Modify-Printer Response:

Group 1: Operation Attributes

4.7 CUPS-Delete-Printer Operation

The CUPS-Delete-Printer operation (0x4004) removes an existing printer from the system.

Note:

This operation requires administrative priviledges and must be POSTed to "/admin/". POSTs to other paths will result in a client-error-not-authorized (IPP_NOT_AUTHORIZED) error.

4.7.1 CUPS-Delete-Printer Request

The following groups of attributes are supplied as part of the CUPS-Delete-Printer request:

Group 1: Operation Attributes

4.7.2 CUPS-Delete-Printer Response

The following groups of attributes are send as part of the CUPS-Delete-Printer Response:

Group 1: Operation Attributes

4.8 CUPS-Get-Classes Operation

The CUPS-Get-Classes operation (0x4005) returns the printer attributes for every printer class known to the system. This may include printer classes that are not served directly by the server.

4.8.1 CUPS-Get-Classes Request

The following groups of attributes are supplied as part of the CUPS-Get-Classes request:

Group 1: Operation Attributes

4.8.2 CUPS-Get-Classes Response

The following groups of attributes are send as part of the CUPS-Get-Classes Response:

Group 1: Operation Attributes

Group 2: Printer Class Object Attributes

4.9 CUPS-Add-Modify-Class Operation

The CUPS-Add-Modify-Class operation (0x4006) adds a new printer class or modifies and existing printer class on the system.

Note:

This operation requires administrative priviledges and must be POSTed to "/admin/". POSTs to other paths will result in a client-error-not-authorized (IPP_NOT_AUTHORIZED) error.

4.9.1 CUPS-Add-Modify-Class Request

The following groups of attributes are supplied as part of the CUPS-Add-Modify-Class request:

Group 1: Operation Attributes

Group 2: Printer Object Attributes

4.9.2 CUPS-Add-Modify-Class Response

The following groups of attributes are send as part of the CUPS-Add-Modify-Class Response:

Group 1: Operation Attributes

4.10 CUPS-Delete-Class Operation

The CUPS-Delete-Class operation (0x4007) removes an existing printer class from the system.

Note:

This operation requires administrative priviledges and must be POSTed to "/admin/". POSTs to other paths will result in a client-error-not-authorized (IPP_NOT_AUTHORIZED) error.

4.10.1 CUPS-Delete-Class Request

The following groups of attributes are supplied as part of the CUPS-Delete-Class request:

Group 1: Operation Attributes

4.10.2 CUPS-Delete-Class Response

The following groups of attributes are send as part of the CUPS-Delete-Class Response:

Group 1: Operation Attributes

4.11 CUPS-Accept-Jobs Operation

The CUPS-Accept-Jobs operation (0x4008) sets the "printer-is-accepting-jobs" attribute to true for the specified printer or printer class.

Note:

This operation requires administrative priviledges and must be POSTed to "/admin/". POSTs to other paths will result in a client-error-not-authorized (IPP_NOT_AUTHORIZED) error.

4.11.1 CUPS-Accept-Jobs Request

The following groups of attributes are supplied as part of the CUPS-Accept-Jobs request:

Group 1: Operation Attributes

4.11.2 CUPS-Accept-Jobs Response

The following groups of attributes are send as part of the CUPS-Accept-Jobs Response:

Group 1: Operation Attributes

4.12 CUPS-Reject-Jobs Operation

The CUPS-Reject-Jobs operation (0x4009) sets the "printer-is-accepting-jobs" attribute to false for the specified printer or printer class.

Note:

This operation requires administrative priviledges and must be POSTed to "/admin/". POSTs to other paths will result in a client-error-not-authorized (IPP_NOT_AUTHORIZED) error.

4.12.1 CUPS-Reject-Jobs Request

The following groups of attributes are supplied as part of the CUPS-Reject-Jobs request:

Group 1: Operation Attributes

Group 2: Printer Object Attributes

4.12.2 CUPS-Reject-Jobs Response

The following groups of attributes are send as part of the CUPS-Reject-Jobs Response:

Group 1: Operation Attributes

4.13 CUPS-Set-Default Operation

The CUPS-Set-Default operation (0x400A) sets the default printer destination for all clients.

Note:

This operation requires administrative priviledges and must be POSTed to "/admin/". POSTs to other paths will result in a client-error-not-authorized (IPP_NOT_AUTHORIZED) error.

4.13.1 CUPS-Set-Default Request

The following groups of attributes are supplied as part of the CUPS-Set-Default request:

Group 1: Operation Attributes

4.13.2 CUPS-Set-Default Response

The following groups of attributes are send as part of the CUPS-Set-Default Response:

Group 1: Operation Attributes

4.14 CUPS-Get-Devices Operation

The CUPS-Get-Devices operation (0x400B) returns all of the supported device-uri's for the server (CUPS 1.1 and higher).

4.14.1 CUPS-Get-Devices Request

The following groups of attributes are supplied as part of the CUPS-Get-Devices request:

Group 1: Operation Attributes

4.14.2 CUPS-Get-Devices Response

The following groups of attributes are send as part of the CUPS-Get-Devices Response:

Group 1: Operation Attributes

Group 2: Device Object Attributes

4.15 CUPS-Get-PPDs Operation

The CUPS-Get-PPDs operation (0x400C) returns all of the locally available PPD files on the system (CUPS 1.1 and higher).

4.15.1 CUPS-Get-PPDs Request

The following groups of attributes are supplied as part of the CUPS-Get-PPDs request:

Group 1: Operation Attributes

4.15.2 CUPS-Get-PPDs Response

The following groups of attributes are send as part of the CUPS-Get-PPDs Response:

Group 1: Operation Attributes

Group 2: PPD Attributes

4.16 CUPS-Move-Job Operation

The CUPS-Move-Job operation (0x400D) moves an active print job to a different printer (CUPS 1.1 and higher).

4.16.1 CUPS-Move-Job Request

The following groups of attributes are supplied as part of the CUPS-Move-Job request:

Group 1: Operation Attributes

Group 2: Job Template Attributes

4.16.2 CUPS-Move-Job Response

The following groups of attributes are send as part of the CUPS-Move-Job Response:

Group 1: Operation Attributes

5 Attributes

CUPS provides many extension attributes to support multiple devices, PPD files, standard job filters, printers, and printer classes.

5.1 Device Attributes

Device attributes are returned by the CUPS-Get-Devices operation and enumerate all of the available hardware devices and network protocols that are supported by the server.

5.1.1 device-class (type2 keyword)

The device-class attribute specifies the class of device and can be one of the following:

5.1.2 device-info (text(127))

The device-info attribute specifies a human-readable string describing the device, e.g. "Parallel Port #1".

5.1.3 device-make-and-model (text(127))

The device-makr-and-model attribute specifies a device identification string provided by the printer connected to the device. If the device or printer does not support identification then this attribute contains the string "unknown".

5.1.4 device-uri (uri)

The device-uri attribute specifies a unique identifier for the device. The actual format of the device-uri string depends on the value of the device-class attribute:

5.2 Job Template Attributes

5.2.1 blackplot (boolean)

The blackplot attribute specifies whether HP-GL/2 plot files should be rendered entirely in black ink (blackplot=true) or using the colors and shades specified in the file (blackplot=false). The default value is false.

5.2.2 brightness (integer(0:200))

The brightness attribute specifies the overall brightness of the printed output in percent. A brightness of 100 is normal, while 200 is twice as bright and 50 is half as bright. The default value is 100.

Brightness is applied to the Cyan, Magenta, Yellow, and Black values using the function "f(x) = brightness / 100 * x".

5.2.3 columns (integer(1:4))

The columns attribute specifies the number of columns to generate when printing text files. The default value is 1.

5.2.4 cpi (type2 enum)

The cpi attribute specifies the number of characters per inch when printing text files. Only the values 10, 12, and 17 are currently supported. The default value is 10.

5.2.5 fitplot (boolean)

The fitplot attribute specifies whether to scale HP-GL/2 plot files to fit on the selected media (fitplot=true) or use the physical scale specified in the plot file (fitplot=false). The default value is false.

5.2.6 gamma (integer(1:10000))

The gamma attribute specifies the luminance correction for the output. A value of 1000 specifies no correction, while values of 2000 and 500 will generate lighter and darker output, respectively. The default value is 1000.

Gamma is applied to the Red, Green, and Blue values (or luminance for grayscale output) using the function "f(x) = x(1000/gamma)".

5.2.7 hue (integer(-180:180))

The hue attribute specifies a color hue rotation when printing image files. The default value is 0.

5.2.8 job-billing (text(MAX))

(CUPS 1.1 and higher)

The job-billing attribute provides a text value to associate with a job for billing purposes.

5.2.9 job-hold-until (keyword | name(MAX))

(CUPS 1.1 and higher)

The job-hold-until attribute specifies a hold time. In addition to the standard IPP/1.1 keyword names, CUPS supports name values of the form "HH:MM" and "HH:MM:SS" that specify a hold time. The hold time is in Greenwich Mean Time (GMT) and not in the local time zone. If the specified time is less than the current time, the job is held until the next day.

5.2.10 job-sheets (1setof type3 keyword | name(MAX))

(CUPS 1.1 and higher)

The job-sheets attribute specifies one or two banner files that are printed before and after a job. The reserved value of "none" disables banner printing. The default value is stored in the job-sheets-default attribute.

If only one value is supplied, the banner file is printed before the job. If two values are supplied, the first value is used as the starting banner file and the second as the ending banner file.

5.2.11 job-originating-host-name (name(MAX))

(CUPS 1.1.5 and higher)

The job-originating-host-name attribute specifies the host from which the job was queued. The value will be the hostname or IP address of the client depending on whether hostname resolution is enabled. The localhost address (127.0.0.1) is always resolved to the name "localhost".

This attribute is read-only.

5.2.12 lpi (type2 enum)

The lpi attribute specifies the number of lines per inch when printing text files. Only the values 6 and 8 are currently supported. The default value is 6.

5.2.13 mirror (boolean)

The mirror attribute specifies whether pages are mirrored on their X axis, which is useful for printing transfer images on special media. The default value is false.

5.2.14 natural-scaling (integer(1:1000))

(CUPS 1.1.9 and higher)

The natural-scaling attribute specifies the scaling of image files with respect to the natural image size. A value of 100 specifies that the image file should exactly the natural size, while 50 is half the natural size and 200 is twice the natural size. The default value is 100.

The ppi option can be used to override the natural resolution of the image, which controls the natural size.

5.2.15 number-up-layout (type2 keyword)

(CUPS 1.1.15 and higher)

The number-up-layout attribute specifies the order each input page is placed on each output page. The following keywords are presently defined:

5.2.16 page-border (type2 keyword)

(CUPS 1.1.15 and higher)

The page-border attribute specifies whether a border is draw around each page. The following keywords are presently defined:

5.2.17 page-bottom (integer(0:MAX))

The page-bottom attribute specifies the bottom margin in points (72 points equals 1 inch). The default value is the device physical margin.

5.2.18 page-label (text(MAX))

(CUPS 1.1.7 and higher)

The page-label attribute provides a text value to place in the header and footer on each page. If a classification level is set on the server, then this classification is printed before the page label.

5.2.19 page-left (integer(0:MAX))

The page-left attribute specifies the left margin in points (72 points equals 1 inch). The default value is the device physical margin.

5.2.20 page-right (integer(0:MAX))

The page-right attribute specifies the right margin in points (72 points equals 1 inch). The default value is the device physical margin.

5.2.21 page-set (type2 keyword)

The page-set attribute specifies which pages to print in a file. The supported keywords are "all", "even", and "odd". The default value is "all".

5.2.22 page-top (integer(0:MAX))

The page-top attribute specifies the top margin in points (72 points equals 1 inch). The default value is the device physical margin.

5.2.23 penwidth (integer(0:MAX))

The penwidth attribute specifies the default pen width in micrometers when printing HP-GL/2 plot files. The default value is 1000 (1 millimeter).

5.2.24 position (type2 keyword)

The position attribute specifies the location of image files on the media. The following keyword values are recognized:

5.2.25 ppi (integer(1:MAX))

The ppi attribute specifies the resolution of an image file in pixels per inch. The default value is the resolution included with the file or 128 if no resolution information is available.

5.2.26 prettyprint (boolean)

The prettyprint attribute specifies whether text files should be printed with a shaded header and keyword highlighting (prettyprint=true) or without additional formatting (prettyprint=false). The default value is false.

5.2.27 saturation (integer(0:200))

The saturation attribute specifies the color saturation when printing image files. A saturation of 100 is normal, while values of 50 and 200 will be half and twice as colorful, respectively. The default value is 100.

5.2.28 scaling (integer(1:1000))

The scaling attribute specifies the scaling of image files with respect to the selected media. A value of 100 specifies that the image file should fit 100% of the page, or as much as possible given the image dimensions. The default value is unspecified.

The scaling attribute overrides the ppi attribute if specified.

5.2.29 wrap (boolean)

The wrap attribute specifies whether long lines should be wrapped (wrap=true) or not (wrap=false) when printing text files. The default value is true.

5.3 PPD Attributes

5.3.1 ppd-natural-language (naturalLanguage)

The ppd-natural-language attribute specifies the language encoding of the PPD file (the LanguageVersion attribute in the PPD file). If the language is unknown or undefined then "en" (English) is assumed.

5.3.2 ppd-make (text(127))

The ppd-make attribute specifies the manufacturer of the printer (the Manufacturer attribute in the PPD file). If the manufacturer is not specified in the PPD file then an educated guess is made using the NickName attribute in the PPD file.

5.3.3 ppd-make-and-model (text(127))

The ppd-make-and-model attribute specifies the manufacturer and model name of the PPD file (the NickName attribute in the PPD file). If the make and model is not specified in the PPD file then the ModelName or ShortNickName attributes are used instead.

5.3.4 ppd-name (name(255))

The ppd-name attribute specifies the PPD filename on the server relative to the model directory. The forward slash (/) is used to delineate directories.

5.4 Printer Attributes

5.4.1 job-k-limit (integer)

(CUPS 1.1 and higher)

The job-k-limit attribute specifies the maximum number of kilobytes that may be printed by a user, including banner files. The default value of 0 specifies that there is no limit.

5.4.2 job-page-limit (integer)

(CUPS 1.1 and higher)

The job-page-limit attribute specifies the maximum number of pages that may be printed by a user, including banner files. The default value of 0 specifies that there is no limit.

5.4.3 job-quota-period (integer)

(CUPS 1.1 and higher)

The job-quota-period attribute specifies the time period used for quota calculations, in seconds. The default value of 0 specifies that the limits apply to all jobs that have been printed by a user that are still known to the system.

5.4.4 job-sheets-supported (1setof type3 keyword | name(MAX))

(CUPS 1.1 and higher)

The job-sheets-supported attribute specifies the available banner files. There will always be at least one banner file available called "none".

5.4.5 printer-type (type2 enum)

The printer-type attribute specifies printer type and capability bits for the printer or class. The default value is computed from internal state information and the PPD file for the printer. The following bits are defined:

BitDescription
0x00000001Is a printer class.
0x00000002Is a remote destination.
0x00000004Can print in black.
0x00000008Can print in color.
0x00000010Can print on both sides of the page in hardware.
0x00000020Can staple output.
0x00000040Can do fast copies in hardware.
0x00000080Can do fast copy collation in hardware.
0x00000100Can punch output.
0x00000200Can cover output.
0x00000400Can bind output.
0x00000800Can sort output.
0x00001000Can handle media up to US-Legal/A4.
0x00002000Can handle media from US-Legal/A4 to ISO-C/A2.
0x00004000Can handle media larger than ISO-C/A2.
0x00008000Can handle user-defined media sizes.
0x00010000Is an implicit (server-generated) class.
0x00020000Is a network default printer.
0x00040000Is a facsimile device.

5.4.6 printer-type-mask (type2 enum)

(CUPS 1.1 and higher)

The printer-type-mask attribute is used to choose printers or classes with the CUPS-Get-Printers and CUPS-Get-Classes operations. The bits are defined identically to the printer-type attribute and default to all 1's.

5.4.7 requesting-user-name-allowed (1setof name(127))

(CUPS 1.1 and higher)

The requesting-user-name-allowed attribute lists all of the users that are allowed to access a printer or class. Either this attribute or the requesting-user-name-denied attribute will be defined, but not both.

5.4.8 requesting-user-name-denied (1setof name(127))

(CUPS 1.1 and higher)

The requesting-user-name-denied attribute lists all of the users that are not allowed to access a printer or class. Either this attribute or the requesting-user-name-allowed attribute will be defined, but not both.

5.5 Printer Class Attributes

5.5.1 member-names (1setof name(127))

The member-names attribute specifies each of the printer-name attributes of the member printers and classes. Each name corresponds to the same element of the member-uris attribute.

5.5.2 member-uris (1setof uri)

The member-uris attribute specifies each of the printer-uri attributes of the member printers and classes. Each URI corresponds to the same element of the member-names attribute.

A Glossary

A.1 Terms

C
A computer language.
parallel
Sending or receiving data more than 1 bit at a time.
pipe
A one-way communications channel between two programs.
serial
Sending or receiving data 1 bit at a time.
socket
A two-way network communications channel.

A.2 Acronyms

ASCII
American Standard Code for Information Interchange
CUPS
Common UNIX Printing System
ESC/P
EPSON Standard Code for Printers
FTP
File Transfer Protocol
HP-GL
Hewlett-Packard Graphics Language
HP-PCL
Hewlett-Packard Page Control Language
HP-PJL
Hewlett-Packard Printer Job Language
IETF
Internet Engineering Task Force
IPP
Internet Printing Protocol
ISO
International Standards Organization
LPD
Line Printer Daemon
MIME
Multimedia Internet Mail Exchange
PPD
PostScript Printer Description
SMB
Server Message Block
TFTP
Trivial File Transfer Protocol