The Complex Question of POS Printer Design
I am considering developing an application to run on POS terminals in addition to the software already installed. I would like it to receive POS printer commands and then intercept and modify some of them. So, for example, when a receipt is printed, we would like to add a special reference number in the middle without changing the third party POS applications.
I'd love to hear people's suggestions on the best way to approach this by reading the POS specs, it doesn't seem trivial.
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I think the solution would be to do this outside of the POS app, but communicate at a level that it understands to print. A solution that looks like a printer to capture data, reformat and then send will do a trick or something that interacts with the OS (let's say Windows) at the printer port level.
On Windows we use a custom port monitor we created for caputre and feed this data, this is what we use internally so I would not suggest it for you as it has some bugs. A similar solution to RedMon . It can provide a solution or give you ideas on how to accomplish it. Once the data is captured, you launch a process against it.
An alternative for the web is that you can configure something like montiors 9100 (RAW) or 515 (LPR) to capture data.
Finally, if it's Windows and you don't want to build something as low-level as RedMon, you can always use named pipes. You must start a service application that will monitor the named pipe. Your POS printer will have a port set to "local" and the port will be \. \ Pipe \. This will allow the application to interact with your service and thus start the process.
You can have multiple named pipes / redmon / network ports, each with a unique associated output to route to the correct device on the other side.
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