What is LPR/LPD?

What is LPR?

LPR stands for Line Print Requestor. It’s the mechanism to ask an LPD printer to print something for you. There are also status commands and a few others.

Other terms for the LPR program include the client program or the print client. Nearly every computer system has at least one LPR print client. We have a page with sample setups for many print clients. These days, it may be easier to do a web search for LPR setup on your target system.

The setup for an LPR print client includes the following necessary information:

  • the computer name or IP address
  • the queue you want to send your print jobs to

What is LPD?

LPD stands for Line Print Daemon. A daemon is another name for a system service. Originally on Unix systems, it was a program that ran in the background.

Your printer might contain LPD software. Microsoft has a free program.

Our product, RPM Remote Print Manager® ("RPM"), fully supports the LPD protocol as well as other print protocols and provides functionality sought by our customers since the 1990s. We actively support RPM, offering new features and updates regularly.

What is the LPD service?

In a general sense, the LPD service is the software that provides an LPD port to connect to and answers requests (including printing) from an LPR print client. RPM is an LPD service, and so is the Microsoft LPD program mentioned above.

This can include printing jobs, displaying status, removing jobs that have not printed, etc.

The LPD service and the term LPD printer are synonymous.

The term "LPD services" can also refer to the Microsoft LPD program.

What port does LPD use?

LPD uses TCP port 515. Typically port 515 is reserved on any networking computer for LPD printing. Sometimes you'll see it displayed in a network status window as "printer".

What does LPR print mean?

If you are using a computer system such as an IBM AS/400 or an HP/UX system, when you print, you may not be using an attached printer. It's likely you direct your print jobs to a printer in your network. Often those print jobs go out using the LPR methodology supported by your vendor.

Similarly, if you use Windows and print from an application, you might use LPR print. Windows printers have a port definition. It's easy to edit an existing printer definition in Windows to use an LPR port, meaning, the Windows spooler sends your print job using LPR to a printer--which could be RPM. Many people use this to extend functionality for their prints, perhaps printing from multiple trays.

What then is an LPR port?

There may not be an exact industry definition for LPR port, but the common usage suggests it is a printer port intended to send print jobs using the LPR protocol we've been discussing. 

What is an LPR queue name?

As mentioned above in the section "what is LPR?" each request to an LPD printer includes a queue name. This way you can use one service to process a wide variety of printing tasks, including entirely distinct setups for a variety of operations.

LPD ports

An LPR port ultimately communicates with an LPD port. Port numbers are unique so that you can be sure your request goes to the right software. The LPD port number is 515. On any given computer, port 515 is used to receive print jobs.

About LPD printing

When I was a researcher in the eighties and nineties, the LPD print server we shared for printing tasks had an array of setups, each with a unique name. The name contained the instructions for printing your particular print jobs according to your requirements.

The HP printers in our office typically have two named queues, one for processing raw data already formatted for the printer, the other for accepting plain-text which the printer renders on its own.

RPM supports the earlier notion of named queues, where you have as many as you want, each with its unique setup instructions.

We've noticed that our customers create distinctive queue names which capture the destination and the process to an extent. With RPM anyone can use the queue names which make sense to them.

For more information on the LPD protocol, please consult RFC 1179, Line Printer Daemon Protocol, dated August 1990, edited by L. McLaughlin III. You can find the RFC documents at http://www.ietf.org/rfc/

For more information on RPM start at RPM intro page, the virtual printer page, or download the 21-day free trial with pre-sales technical support, or contact us.