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Apple II
Technical Notes
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Developer Technical Support
AppleTalk
#3: Avoiding Remote Printer Time-Outs
Revised by: Jim Luther September 1989
Written by: Jim Luther May 1989
This Technical Note discusses how to avoid time-outs when printing to remote
printers.
Changes since May 1989: Updated to reflect System Software 5.0 changes
and to clarify the results of changing the time-out interval.
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The Apple II AppleTalk firmware's Remote Print Manager (RPM), which supports
AppleTalk's Super Serial Card (SSC) entry points, maintains a time-out
interval value. The time-out interval is usually set to 30 seconds. When an
application quits writing to the AppleTalk firmware, the RPM waits this time
interval before sending the last block of data to the printer and closing the
Printer Access Protocol (PAP) connection.
What does this mean? If an application waits longer than the time-out
interval (e.g., 30 seconds) between any write accesses to the AppleTalk
firmware (i.e., a pause between initialization and printing or a pause during
printing), the PAP connection closes, the current page may be ejected from the
printer (this is printer dependent--the ImageWriter II and ImageWriter LQ do
not automatically eject the page, the Apple LaserWriter does), and the rest of
the application's output to the printer is lost. If you initialize the
AppleTalk SSC firmware, you must print immediately or a time-out may occur and
reinitialization is necessary to print again. Applications should not
initialize the firmware and expect it still to be initialized at a later point
in time.
What You Can Do
The RPM's PMSetPrinter call may be used to change the time-out interval to a
different value. However, the time-out interval should be kept as short as
possible because other users cannot open another PAP connection with the
printer until your machine has timed-out. In other words, if you set the
time-out interval for five minutes, the RPM keeps the PAP connection open with
the printer for five minutes after the last character is written to the RPM,
thus blocking other machines from using that printer for five extra minutes;
this delay is unacceptable in a shared printer environment.
With an Apple IIGS using System Software 5.0, the RPM's PMSetPrinter call may
be used to set the time-out interval to zero. When the time-out interval is
set to zero, the session never times out and must be closed with the Apple
IIGS-specific PMCloseSession RPM call.
Further Reference
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o AppleShare Programmer's Guide for the Apple IIGS