The following topics can help you learn more about controlling the VNA using SCPI and the GPIB.
COM versus SCPI
GPIB Fundamentals
The Rules and Syntax of SCPI Commands
Configure for SCPI / SICL over GPIB
Calibrating the VNA Using SCPI
Getting Data from the VNA using SCPI
The VNA as a USB Device
Remote Control of SCPI USB Devices Connected to a VNA
Reading the VNA Status Registers
Referring to Traces, Measurements, Channels, and Windows Using SCPI
Synchronizing the VNA and Controller
Shut Down the VNA Remotely