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## Simple Spooler 0.4 ## |
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Copyright (c) 2026, Ken McLeod. |
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This application acts as a virtual printer on an AppleTalk network, receiving |
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print jobs using PAP (Printer Access Protocol) and spooling them to files. It |
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can either print immediately or at a later scheduled time, sending the print |
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job to a locally-connected ImageWriter printer which would otherwise not be |
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visible on the network. |
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Simple Spooler is freeware. You may use and distribute the software at no |
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charge. See the LICENSE file for conditions on your use of the source code. |
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No AI or LLM was used at any stage of creating this software. There is no |
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substitute for the knowledge that is gained through personal experience. |
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**System requirements** |
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System 6.0 or later (up to Mac OS 9.2.2) is currently required to run Simple |
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Spooler. This software has been tested on System 6.0.5, 7.0.1, and 7.5.3, as |
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well as Mac OS 8.6 and 9.2.2. |
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AppleTalk must be set to Active in the Chooser. You should have enough free |
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disk space on your startup disk to accomodate the print jobs you expect to |
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receive. ImageWriter spool files occupy less space than LaserWriter spool |
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files, but all can add up if they are not being processed immediately. |
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**Starting the spooler** |
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After opening the application for the first time, a dialog will present the |
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following options (also available from "Settings..." in the Control menu): |
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* Printer name |
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Type a name for the print spooler, which you can think of as a virtual |
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printer. This name will appear on the network and can be selected by other |
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users as an AppleTalk printer in the Chooser. |
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* Auto-run at launch |
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Select this checkbox if you want the spooler to run automatically when the |
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application opens, rather than needing to manually click Start. This allows |
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for unattended server operation, e.g. by placing an alias to Simple Spooler |
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in your Startup Items folder on System 7.0 or later. |
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* Virtual printer type |
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Select one of the icons representing LaserWriter, ImageWriter LQ, or |
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ImageWriter to create a virtual printer of that type. For an ImageWriter or |
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LQ, you can additionally select whether the printer is seen as having a |
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color ribbon or a sheet feeder. The "IW1 compatibility" checkbox improves |
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compatibility with the original ImageWriter I by removing newer printer |
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control codes that only the ImageWriter II understands. The "Skip Reverse |
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Feeds" checkbox strips control codes that would cause your printer to roll |
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the paper backwards; selecting this can prevent misprints and paper jams. |
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* Print to this port |
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Select the icon for the local serial port where your ImageWriter printer |
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is connected. If the Enabled checkbox is selected, spooled print jobs will |
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automatically be printed to this port once they have been received, as long |
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as the current time is within the scheduled printing hours. The default |
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setting is 12 AM - 12 AM (or 0 - 24), an unrestricted span of 24 hours |
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starting at midnight. |
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You can restrict printer use by using the up/down arrow control to change the |
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start and end times; for example, you may only want printing to occur during |
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business hours and not at night. If the spooler receives a print job outside |
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the specified hours, it will be printed later once the start hour is reached. |
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Uncheck the Enabled box if you don't have a local printer connected, or if you |
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just want to hold all jobs for printing at a later date. |
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Click Start to begin running the spooler. This registers the printer name you |
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provided on the AppleTalk network, listens for incoming print jobs, and |
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prepares to print any previously spooled jobs in its spool folder. |
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**Stopping the spooler** |
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The spooler can be stopped by selecting "Stop Spooler" from the Control menu, |
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or by quitting the application. |
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**Printing to the spooler** |
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On a Mac connected to your AppleTalk network, open Chooser and select the |
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printer driver for the printer type being emulated. For example, if Simple |
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Spooler is emulating an AppleTalk ImageWriter, then select the "AppleTalk |
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ImageWriter" icon in Chooser. You should see the spooler appear as a printer |
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in the list. After selecting it and closing the Chooser window, you should be |
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able to print to the spooler from any application. |
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**About the log** |
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Simple Spooler displays a single window with a log of its activity. This log is |
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entirely in memory, and does not persist when the application quits. To avoid |
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running out of memory, the earliest entries are deleted periodically as new |
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ones are added to the end. |
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By default, messages are logged when the spooler starts up or stops, when |
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incoming connections are handled, when spooled jobs are printed, or if an error |
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occurs. However, more details can be enabled to aid in debugging. There are four |
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log levels, each printing its own messages as well as those of the levels below |
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it. Level 0 is the default. At level 1, internal activity and warnings are |
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logged. At level 2, all protocol messages are displayed, and at the maximum |
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level 3, additional debug data is logged. |
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Because changing the log level to 2 or higher will greatly diminish server |
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performance, and the extra information is intended for development purposes |
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only, there is no menu item for this hidden feature. Press the command-shift-L |
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key combination to increase the log level by 1. After reaching 3, the log |
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level will reset to 0 again. The spooler should normally be run only at the |
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default log level 0. |
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Pressing the command-shift-S key combination will output the server's current |
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status to the log. Alternatively, select Print Status from the Control menu. |
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**About the print queue** |
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The first time Simple Spooler is run, it will create a spool folder (named |
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Simple Spooler) in the Preferences folder within the System Folder, or in the |
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System Folder itself if prior to System 7.0. Print jobs are saved as temporary |
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files in the spool folder. Their file names start with a prefix that depends on |
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the printer type selected: IW for ImageWriter, LQ for ImageWriter LQ, and LW for |
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LaserWriter. When the spooler is running, it checks periodically for files in |
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this folder which have the file type 'pjob', whose names start with the current |
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prefix and a hyphen, and do not end in a .ps extension. For example, a file |
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named "IW-12345" will be printed, but not "IWEm" or "IW12345" or "IW-12345.ps". |
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Spool files are processed in the order they were added to the folder. If the |
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Enabled checkbox was selected and printing is currently enabled, the file is |
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sent to the selected serial port. Once all bytes in the spool file have been |
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sent to that port without an error, that job is considered complete and the file |
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is deleted. |
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**About LaserWriter spooling** |
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This application was primarily designed to emulate an ImageWriter printer, but |
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it can also create a virtual LaserWriter which spools its print jobs to |
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PostScript files. This feature is somewhat redundant, as you could just select |
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"print to file" in the LaserWriter print dialog to obtain the same result. An |
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ImageWriter cannot render PostScript code, but older LaserWriter models with a |
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serial port connection can theoretically be used to print spooled files; this |
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has not been tested. |
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Note: you can use software such as Ghostscript, Adobe Illustrator, or even |
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Preview.app (on older versions of Mac OS X) to view PostScript files, or convert |
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them to another format for viewing on a modern computer. |
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**Generating PostScript output from ImageWriter print jobs** |
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If you would like to have print jobs for an ImageWriter automatically generate |
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PostScript output files, simply copy the "IWEm" file from this distribution into |
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the spool folder. "IWEm" (ImageWriter Emulator) is PostScript code from Apple |
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that can interpret ImageWriter print sequences. When a print job is received |
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successfully, and the file "IWEm" is found in the spool folder, a second file |
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with a .ps extension will also be created and appear in the folder. This .ps |
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file can be viewed in applications which support PostScript. |
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Note: IWEm is not compatible with color printing, or with the ImageWriter LQ's |
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Best and Faster modes. A better option for converting ImageWriter spool files |
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into a format that can be viewed on a modern computer is the 'imagewriter' |
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command line tool, available from <https://github.com/greg-kennedy/ImageWriter>. |
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**Using Simple Spooler in a Mac emulator** |
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If you don't want to keep a real Mac and ImageWriter turned on for hours, you |
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can run Simple Spooler in a virtual Mac with emulation software such as QEMU, |
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Mini vMac, or Snow that supports AppleTalk networking. Be aware that printing to |
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a serial port where nothing is actually connected sends those bytes to nowhere. |
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You may want to uncheck the Enabled box for printing to a serial port when |
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running Simple Spooler in an emulator, and instead copy the spool files over to |
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your real Mac's spool folder when you are ready to print them. |
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**Known issues** |
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Printing to the spooler from the same Mac which is running the spooler does not |
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work well yet. (There's a bug with self-send mode. Don't try it unless you like |
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rebooting.) |
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On System 6, there are some errors being logged with the tickle mechanism which |
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is part of PAP. This should be fixable and does not seem to affect printing. |
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There is currently no handshaking with the real printer before attempting to |
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print, so if no printer is connected to the selected port, data is sent into the |
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void without any error and the spool file is deleted. |
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In this release, LaserWriter spooling is only known to work with version 8.3.4 |
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of the LaserWriter 8 driver. This is the version which shipped with system |
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software 7.5.3. Version 8.6.1 and later send an additional query prior to normal |
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setup, as does 7.1.1 and likely others. In general, we can't yet handle more |
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than one query transaction (meaning the driver is asking us to answer its |
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questions, rather than giving us data) in a given print job. A fix is being |
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investigated. |
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**Bug reports, feedback, etc.** |
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Please let me know about your experience with Simple Spooler, especially if you |
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run into any problems. This prerelease software is still under development and |
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not yet considered stable. Bug reports and suggestions for improvement are |
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always welcome. (When reporting a problem, please mention the system version, |
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spooler configuration, and what software you are using to print, so I can try |
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to reproduce it.) Thanks! |
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<https://mastodon.social/@_the_cloud> |
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<thecloudexpanse @gmail.com> |
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**Modification history** |
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0.1 2026-02-16: first release for testing |
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0.2 2026-02-23: added ImageWriter 1 compatibility mode |
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0.3 2026-07-30: split up configuration and startup, so server can auto-run; |
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rewrote filter to run when printing rather than spooling; |
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optionally strip reverse feeds so paper never rolls back |
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0.4 2026-08-06: fix bug that failed to remove a filtered byte if it was the |
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last byte in the buffer being processed; |
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strip extra linefeeds generated by a reverse feed; |
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reset printer to defaults before starting each print job |