INT 6F - 10NET v5.0 - "WHO" - ENUMERATE USERS ON NETWORK
        AH = 8Dh
        BX = service mask (see below)
        CX = length of buffer
        DS:DX -> buffer for array of Who data structures (see below)
Return: CF clear if successful
            CX = number of nodes matching service mask
            DS:DX buffer filled
        CF set on error
            AX = status (see AH=00h)
SeeAlso: AH=0Dh

Bitfields for service mask:
 bit 0  workstation
 bit 1  file server
 bit 2  print server
 bit 3  de-spool server

Format of Who data structure:
Offset  Size    Description
 00h  8 BYTEs   user name
 08h 15 BYTEs   node ID
 17h  3 BYTEs   unique portion of Ethernet address
 1Ah    BYTE    Who group number
 1Bh    WORD    service mask (see above)
 1Dh    DWORD   serial number
 21h    BYTE    maximum concurrent users with same serial number allowed on net
 22h    BYTE    chat mask (see below)
 23h    BYTE    internal system bits (see below)
 24h  9 BYTEs   version number in format MM.mm.xxx
 2Dh    BYTE    number of shared directories
 2Eh    BYTE    number of shared printer queues

Bitfields for chat mask:
 bit 0  chat permitted
 bit 1  bell enabled
 bit 2  chat keyboard initiated
 bit 3  in INT 16 handler
 bit 4  in Get Input
 bit 5  display has timed out
 bit 6  chat is idle

Bitfields for internal system bits:
 bit 0  submit permitted
 bit 1  submit initiated
 bit 2  submit executing
 bit 3  internal client call/chat/spool/autospool
 bit 4  in spool termination
 bit 5  print permitted
 bit 6  waiting for keyboard input

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