The barcode can be decoded. mbarcode gives the right number when I scan the barcode on the packet. The DHL webpage is http://www.dhl.de/de.html You can also switch to an english version at the top of the page http://www.dhl.de/en.html
I don´t know much about the other packet services like hermes or DPD or UPS. They all have tracking service on their pages. But what´s about the barcode? I´m only used to send packets via dhl.