INT 21 - PC/TCP IPCUST.SYS - RESET CONFIGURATION DATA READ POINTER
        AX = 4402h
        BX = file handle referencing device "$IPCUST"
        CX, DS:DX ignored
Return: CF clear if successful
            AX destroyed
        CF set on error
            AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:   there are a total of 378h bytes of configuration data for IPCUST.SYS
          version 2.05.  If less than the entire data is read or written,
          the next read/write continues where the previous one ended; this
          call and AX=4403h both reset the location at which the next
          operation starts to zero
SeeAlso: AH=40h"IPCUST",AX=4403h"IPCUST"