VIANET DOS3 and IBM PC NETWORK EMULATION


         CAUTION: The Access Mode specification for the 3DH
         (OPEN) call is different for DOS 3 than for ViaNet. Use
         the IBM protocol for this call when using ViaNet DOS 3
         call emulation or when running with DOS 3.0 or DOS 3.1.

    All nodes on a network must run with the same level of ViaNet
    software. When ViaNet is brought up at a node, the default is for
    DOS 3 call emulation to be disabled. This default may be changed
    using SERIALIZ.EXE version 1.20.02. DOS 3 call emulation may be
    enabled or disabled at any node without affecting network
    operations.

         NOTE: DOS 3 eumlation is automatically enabled when the
         host DOS is release 3.0 or greater. It is not possible
         to disable DOS 3 call emulation when the host DOS
         release is 3.0 or greater.

    ViaNet supports DOS 3 call emulation enable/disable by means of a
    switch for the NET command. The slash (/) in the following
    examples represents the DOS switch character. The DOS switch
    character is user selectable.

    To enable DOS 3 call emulation:

         NET /3

    To disable DOS 3 call emulation:

         NET /2

         NOTE: The NET /3 option may be specified with the
         optional parameter V (NET /3v). When the optional
         parameter V is used with the /3 option the DOS 'Get DOS
         version number' call (INT 21H function 30H) returns
         3.1.

    When DOS 3 call emulation is enabled, the following Interrupt 21H
    function calls are supported by ViaNet as implemented for IBM PC-
    DOS. Use the IBM protocol for the following calls. Refer to the
    3.1 DOS Reference Manual for details.

         INT 2FH     
         FUNCTION    DESCRIPTION

         0000H       Check if multiplex interrupt (INT 2F) interface
                     installed
                     Support only includes a value of zero (0) in AL.
                     Any other value in AL results in error code 5
                     being returned
                          RETURN: AL = 1 (installed)

         0100H       Get installed state of resident part of PRINT
                     Support only includes a value of zero (0) in AL.
                     Any other value in AL results in error code 5
                     being returned
                          RETURN: AL = 1 (not installed and not
                     permitted)





         B8H         Net command installation
                     Support includes the following function value
                     allowed in AL:
                          00H - Check if Net program is installed
                                  RETURN: AL = FF (installed)
                                                BX = 48 (server,
                                  redirector)

         INT 21H     
         FUNCTION    DESCRIPTION

         3DH         Open file with sharing specified

         44H         I/O control for devices (IOCTL).
                     Support includes the following function values
                     allowed in AL:
                          08H - Is a particular block device
                                changeable?
                          09H - Is a particular block device
                                redirected?
                          0AH - Is a particular handle redirected?
                          0BH - Change sharing retry count.

         59H         Get extended error

         5AH         Create temporary file with unique name

         5BH         Create new file

         5CH         Lock/Unlock file access.
                     Support includes the following function values
                     allowed in AL:
                          00H - Lock byte range
                          01H - Unlock byte range

         5E00H       Get machine name Access

         5E02H       Set printer setup
                          ViaNet returns success although the printer
                          setup is not set.

         5E03H       Get printer setup
                          Always returns success and indicates a zero
                          length printer setup

         5F02H       Get redirection list entry

         5F03H       Redirect device

         5F04H       Cancel redirection

         62H         Get PSP address

    If any of the above DOS 3 calls other than INT 21H Function 3DH
    and INT 2FH Functions 0000H and 0100H are used when DOS 3 call
    emulation is not enabled, the call causes an error message and a
    return code (01H) indicating an invalid function number.