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Line Printer Daemon protocol
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LPR/LPD
(Line Printer Remote/Line Printer Daemon) A TCP/IP printing protocol and network print server. Originally developed for Berkeley Unix (BSD Unix), LPR/LPD was the de facto standard for Unix printing prior to LPRng, IPP and CUPS. Used in conjunction with a printer driver, the LPR/LPD server queues the files and prints them when the printer becomes available. LPR/LPD servers can support multiple printers, in which case, the client identifies the intended printer by its queue name.
In order to provide a complete printing system, LPR/LPD is used with a printer driver that converts the data into the command format required by the printer.
The Protocol
Comprising only five commands: print, cancel, show status, show long (verbose) status and reset, the LPD protocol is supported in many network printers. Note that the protocol may be used with other print servers, not just LPR/LPD servers.
LPR or LPD?
The terms LPR, LPD and LPR/LPD are used synonymously. LPR was originally the name of the software, and LPD was the name of the daemon (agent) that waited for requests in the server. Therefore, LPR and LPD are both used to refer to the print server software, while LPD typically refers to the protocol. See LPRng, IPP and CUPS.
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Line Printer Daemon protocol
The Line Printer Daemon protocol/Line Printer Remote protocol (or LPD, LPR) is a network protocol for submitting print jobs to a remote printer. The original implementation of LPD was in the Berkeley printing system in the BSD UNIX operating system; the LPRng project also supports that protocol. The Common Unix Printing System (or CUPS), which is more common on modern Linux distributions, supports LPD as well as the Internet Printing Protocol (IPP). Commercial solutions are available that also leverage Berkeley printing protocol components, where more robust functionality and performance is necessary than is available from LPR/LPD (or CUPS) alone (such as might be required in large corporate environments). The LPD Protocol Specification is documented in RFC 1179.[1]
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Usage
A server for the LPD protocol listens for requests on TCP port 515. A request begins with a byte containing the request code, followed by the arguments to the request, and is terminated by an ASCII LF character.
An LPD printer is identified by the IP address of the server machine and the queue name on that machine. Many different queue names may exist in one LPD server, with each queue having unique settings. Note that the LPD queue name is case sensitive. Some modern implementations of LPD on network printers might ignore the case or queue name altogether and send all jobs to the same printer. Others have the option to automatically create a new queue when a print job with a new queue name is received. This helps to simplify the setup of the LPD server.[2] Some companies (e.g. D-Link in model DP-301P+) have a tradition of calling the queue name “lpt1” or “LPT1”.
A printer that supports LPD/LPR is sometimes referred to as a "TCP/IP printer" (TCP/IP is used to establish connections between printers and clients on a network), although that term would be equally applicable to a printer that supports the Internet Printing Protocol.
References
See also
- Lp (Unix)
- LPRng
- Legacy printing
- Common Unix Printing System (CUPS)
- RLPR
- System V printing system
- Spooling
- Print server
- Application layer
- Foomatic
External links
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
