AX = 5FB0h
BX = server login entry index
DS:SI -> buffer for active user entry (see below)
ES:DI -> ASCIZ machine name in form "\\server"
Return: CF clear if successful
CF set on error
AX = error code
BX = next login index

Format of active user entry:
Offset  Size    Description
00h    WORD    virtual circuit number
02h    BYTE    login state
bit 0: fully logged in
1: remote program load login
2: user has system manager privileges
3: user can create audit entries
4: bypass mail protection
5: treat as local process
6: bypass queue protection
7: bypass access control lists
03h    BYTE    last command issued (see below)
04h  5 BYTEs   number of I/O bytes (40-bit unsigned number)
09h  3 BYTEs   number of server requests (24-bit unsigned)
0Ch 16 BYTEs   name of user who is logged in
1Ch 16 BYTEs   name of remote logged in machine
2Ch    BYTE    extended privileges (v4+???)
bit 0: user cannot change his password
2Dh    WORD    time left in minutes (0000h = unlimited) (v4+???)

Values for last command:
00h    login
01h    process termination
02h    open file
03h    close file
04h    create file
05h    create new file
06h    create unique file
07h    commit data to disk
08h    read file
09h    write file
0Ah    delete file
0Bh    set file attributes
0Ch    lock byte range
0Dh    unlock byte range
0Eh    create subdirectory
0Fh    remove subdirectory
10h    rename file
11h    find first matching file
12h    find next matching file
13h    get disk free space
14h    get a queue entry
15h    set a queue entry
16h    control the queue
17h    return login information
18h    return link description
19h    seek on file
1Ah    get server's time
1Bh    create audit entry
1Ch    open file in multitude of modes
1Dh    change password
1Eh    disable account
1Fh    local server file copy
20h    get username from account file
21h    translate server's logical path
22h    make indirect file
23h    get indirect file contents
24h    get physical printer status
25h    get logical print stream info
26h    set logical print stream info
27h    get user's account record
28h    request server shutdown
29h    cancel server shutdown
2Ah    stuff server's keyboard
2Bh    write then commit data to disk
2Ch    set extended queue entry
2Dh    terminate user from server
2Eh    enable/disable logins
2Fh    flush server caches
30h    change username
31h    get extended queue entry
(same as get queue, but can return named fields blanked)