Int 21 Fn 3F  - PC/tcp Ipcust.sys - Read Configuration Data                [N]

   AH = 3Fh
   BX = handle for character device "$IPCUST"
   CX = number of bytes to read
   DS:DX -> buffer for configuration data (see below)

Return: CF clear if successful
       AX = number of bytes actually read
   CF set on error
       AX = error code (05h,06h) (see AH=59h)

Notes: if less than the entire data is read or written, the next read/write
     continues where the previous one ended; IOCTL calls AX=4402h and
     AX=4403h both reset the location at which the next operation starts
     to zero
   the data pointer is also reset to zero if the previous read or write
     reached or exceeded the end of the data, when the current function
     is read and the previous was write, or vice versa
   v2.1+ uses a new configuration method, but allows the installation
     of IPCUST.SYS for backward compatibility with other software which
     must read the PC/TCP configuration

See Also: AH=40h"IPCUST",AX=4402h"IPCUST",AX=4402h"FTPSOFT"

Format of configuration data:
Offset Size    Description
 00h 12 BYTEs  IPCUST.SYS device driver header
 12h   BYTE    ???
 13h   BYTE    ???
 14h   WORD    ???
 16h   BYTE    bit flags
       bit 0: send BS rather than DEL for BackSpace key
       bit 1: wrap long lines
 17h   BYTE    ???
 18h 64 BYTEs  ASCIZ hostname
 58h 64 BYTEs  ASCIZ domain name
       (fully qualified domain name is hostname.domain-name)
 98h 16 BYTEs  ASCIZ username
 A8h 64 BYTEs  ASCIZ full name
 E8h 64 BYTEs  ASCIZ office address
128h 32 BYTEs  ASCIZ phone number
148h   WORD    offset from GMT in minutes
14Ah  4 BYTEs  ASCIZ timezone name
14Eh   WORD    number of time servers
150h  ? DWORDs (big-endian) IP addresses for time servers
   ???
164h   WORD    number of old-style name servers
166h  3 DWORDs (big-endian) IP addresses for name servers
172h   WORD    number of domain name servers
174h  3 DWORDs (big-endian) IP addresses for domain name servers
180h   DWORD   (big-endian) IP address of default gateway
184h   DWORD   (big-endian) IP address of log server
188h   DWORD   (big-endian) IP address of cookie server
18Ch   DWORD   (big-endian) IP address of lpr server
190h   DWORD   (big-endian) IP address of imagen print server
194h 54 BYTEs  ???
1E8h   WORD    TCP default window size in bytes
1EAh   WORD    TCP low window size
1ECh 64 BYTEs  ASCIZ host tabel filename
22Ch  2 BYTEs  ???
22Eh 80 BYTEs  ASCIZ mail relay host name
27Eh   BYTE    ???
27Fh   BYTE    ??? bit flags
280h 44 BYTEs  ???
2ACh   WORD    ???
2AEh 202 BYTEs ???