GC420d does not have networking capability. It needs to connect to a host computer through USB or parallel interface in order to print. The printer itself can accept ZPL from host computer to print. Or, the host computer can send a general printer job to the printer, as if the GC420d was a regular printer. In this case, the GC420d driver needs to be installed on the host printer. You can check out the Link-OS Multiplatform SDK for developing an application on the host. Please be aware that this SDK is for Link-OS printers. The GC420d is not a Link-OS printer. However, the connection part of the SDK should work for USB connectivity with GC420d. The other advanced API in the SDK will not work with GC420d though. Hope this helps.
Here are some additional information regarding your questions.
- Your understanding is correct. Zebra has not included GC420d in its testing yet with Browser Print. But it is a ZPL language printer. So eventually we could try to use Browser Print with GC420d over USB from a host.
- We should be able to use our Link-OS SDK. The only recommendation is that we must use the ZebraPrinter interface, instead of using the ZebraPrinterLinkOs interface, because GC420d is not a Link-OS printer. For developing application for PC, the documentation folder we should use is PC(Java) or PC(.NET). For PC(Java) , the ZebraPrinter interface is at ZebraPrinter.
- Not sure if you have seen this page - Zebra Web Printing Solutions, which contains a suite of information that you may be interested in.
Hope this helps.