Archive for November, 2010

Barcode Printing from the Web

Wednesday, November 24th, 2010

barcodeAt Llamawerx, we’ve been involved with barcode printers since 2003. Our very first project, Cryotrax, required us to drive a Brady barcode printer. That first application was written in Java with Datamax Programming Language (DPL) strings sent serially to the printer.

Fast forward seven years and Cryotrax2 was on the horizon. The printer is the same, but now the application lives in a web-browser and it’s not so simple to send DPL commands to the printer. Doug Griswold, CEO of Llamawerx explains:

The languages of the web, HTML and Javascript, don’t allow you to communicate directly with a serial printer. We wanted to send from any web-browser to the barcode printer without going through a server or requiring a plug-in.  Since the application makes use of AJAX we thought maybe we could install a web-server on the local machine – a server-on-a-client if you will. Then reality hit and we figured a full featured web-server with server-side scripting might be too much. Previous work with Python triggered another idea. Why not use the HTTP server built into Python, mash that up with pySerial, compile with py2exe? Voilà,  HTTP transports DPL commands to the printer. A minor workaround for AJAX cross site scripting and we had a solution.

Unique requirements demand innovative solutions. At Llamawerx we draw on 25+ years of software development using embedded systems, client-server, relational database and web technologies giving us a broad platform to build on.

To learn more about specific technologies in the Llamawerx tool chest, visit or contact us at

PayPal Integration

Monday, November 15th, 2010

Llamawerx has completed several projects integrating PayPal with existing web sites and custom web applications. In some cases, we have integrated products and the PayPal shopping cart into an e-commerce site. On others, we’ve relied on PayPal’s notification API.

Buy Now Buttons

In some instances, our clients want to sell a single product on through their website – for example, a book. The simplest way to do that was to create a PayPal button in their account and use the PayPal generated HTML on the site. Simple, straightforward, effective. The PayPal account holder receives an email when payment is made and ships the product.

Shopping Cart

Another scenario exists when clients want to sell multiple products from the site. One could generate multiple buttons as we did in the simple case and paste them into the site. As you add products, this becomes tedious to manage and the look-and-feel of the buttons won’t match your site. Our solution is to decompose the HTML variables and program custom pages with HTML and PHP. The clicks invoke the PayPal shopping cart, payment is made and the client receives email notification.

Payment Notification

Other clients needed to use PayPal for registration information. This posed a different problem because we needed real-time confirmation that the user paid before offering them access. PayPal offers payment notification through Instant Payment Notification or IPN. By using the IPN API and managing the responses from PayPal, we capture the responses and update the database in real-time thus ensuing timely registration for the events.

PayPal offers a simple platform for sellers looking to move to the Internet. For unique applications, the programming hooks allow integrators to expand the basic offering into a custom solution.