When printing labels using techShip via API connection, we expect the WMS to request the labels, we will generate them and pass back to the WMS. 

In many cases you have an option to request the format - ZPL, PNG, PDF - yet in every case, the printing is done by the WMS.

In this case the WMS should also pass the printer id in the request for the label.

Packing slips are returned via API and will return label with PURPOSE=PACKINGSLIP

For additional and API specific information, refer to: