Android print on Citizen printer (zebra mode) conntected on print server

Hello

I'm trying to print Bitmap from android demo application ZSDK_DemosAndroid, but only empty sticker coming out from printer.

Attached is the java class.

I'm wonder, is the fact that this is USB printer,  connected on the print server?

I've succeeded to print from Windows Mobile application, and from Motorola devices, but from android I've bumped on this problem.

Can you please help me?

Printer: Citizzen, CL-S621 (Zebra mode)

Language is ZPL

Thank you.