Controlling printing through credits

Hi,

I am writing an Internet Cafe application and have mostly all of it complete.
However, I am trying to implement a chargeable printing module.

I want customers to be able to buy 'Printing Credits' and then only be able to print if they have adequate credits.
This must work for all applications, so presumably must require some API work.

i.e.  No matter what application the user is in (Word, Notepad, IE etc), when they click Print, I need to be able to either allow the print or reject it if they don't have the required credits.  At this stage, I am not concerned with details such as whether or not the print job is in colour, but I must know how many pages are being printed.

Thanks in advance,

James.
James_AndrewsAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Mike TomlinsonHigh School Computer Science, Computer Applications, and Mathematics TeachersCommented:
Here is a tutorial page to get you started on the monitoring side of the app.

http://www.merrioncomputing.com/Programming/WatchPrinter.htm
MerrionCommented:
Do the users log in with distinct login names?  If not you may have some difficulty determining who printed what...

IMO the best way to prevent printing once a users credit has expired is to remove him/her from the printers DACL so they have no rights to print.  Any solution that relies on deleting jobs may cause a high load on the print server and might even miss jobs being printed...
James_AndrewsAuthor Commented:
Thanks guys,

I can't really add users to a group because that would allow them to print as many pages as they like.  Also, don't NT group permissions take effect at the next login (when the NT sec token is issued)?

What about creating a Virtual print device which did the job filtering and passes authorised jobs to the real print device?
Big Business Goals? Which KPIs Will Help You

The most successful MSPs rely on metrics – known as key performance indicators (KPIs) – for making informed decisions that help their businesses thrive, rather than just survive. This eBook provides an overview of the most important KPIs used by top MSPs.

MerrionCommented:
One of our clients has implemented a similar type of system by intercepting the Job_Added event and setting the print job's start time and endtime to just before midnight.  This allows the job to spool fully but it doesn't start printing out.  Then you check the number of pages and decide if it is over quota.  If so you delete the print job, if not you unset the print job start and end time so it then prints out.
James_AndrewsAuthor Commented:
Thanks for the quick response.

Is there a non .Net version of the MCL Printer Monitor Component?
MerrionCommented:
I'm afraid not - there is a freeware source (in two parts) in VB6 at http://groups.yahoo.com/group/MerrionComputing/

Files are called PrintWatchServer.zip and PrintWatchClient.zip...could probably be adapted for your requirement?

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Visual Basic Classic

From novice to tech pro — start learning today.