The PORT_VAR_CONTAINER structure provides information for supported printer port monitors.<5>

 typedef struct _PORT_VAR_CONTAINER {
   DWORD cbMonitorData;
   [size_is(cbMonitorData), unique, disable_consistency_check] 
     BYTE* pMonitorData;

cbMonitorData: The size, in bytes, of the buffer that is pointed to by the pMonitorData member.

pMonitorData: An optional pointer to a block of data that is passed to the port monitor.