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
Comprised of 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.