General method.

        ES:BX -> Network Control Block (see below)

        Return: AL = status
                     00h successful
                     01h bad buffer size
                     03h invalid NETBIOS command
                     05h timeout
                     06h receive buffer too small
                     08h bad session number
                     09h LAN card out of memory
                     0Ah session closed
                     0Bh command has been cancelled
                     0Dh name already exists
                     0Eh local name table full
                     0Fh name still in use, can't delete
                     11h local session table full
                     12h remote PC not listening
                     13h bad NCB_NUM field
                     14h no answer to CALL or no such remote
                     15h name not in local name table
                     16h duplicate name
                     17h bad delete
                     18h abnormal end
                     19h name error, multiple identical names in use
                     1Ah bad packet
                     21h network card busy
                     22h too many commands queued
                     23h bad LAN card number
                     24h command finished while cancelling
                     26h command can't be cancelled
                     FFh NETBIOS busy

        Format of Network Control Block:

                 Offset Size  Description
                  00h   BYTE  ncb_command (see below)
                  01h   BYTE  ncb_retcode
                  02h   BYTE  ncb_lsn
                  03h   BYTE  ncb_num
                  04h   DWORD -> ncb_buffer
                  08h   WORD  ncb_length
                  0Ah 16 BYTEs ncb_callname
                  1Ah 16 BYTEs ncb_name
                  2Ah   BYTE  ncb_rto
                  2Bh   BYTE  ncb_sto
                  2Ch   DWORD -> ncb_post  /* int (far *ncb_post)(); */
                  30h   BYTE  ncb_lana_num
                  31h   BYTE  ncb_cmd_cplt
                  32h 14 BYTEs ncb_reserve

        Values for ncb_command field in NCB (or with 80h for
        non-waiting call):

                 10h start session with NCB_NAME name (call)
                 11h listen for call
                 12h end session with NCB_NAME name (hangup)
                 14h send data via NCB_LSN
                 15h receive data from a session
                 16h receive data from any session
                 17h send multiple data buffers
                 20h send unACKed message (datagram)
                 21h receive datagram
                 22h send broadcast datagram
                 23h receive broadcast datagram
                 30h add name to name table
                 31h delete name from name table
                 32h reset adapter card and tables
                 33h get adapter status
                 34h status of all sessions for name
                 35h cancel
                 36h add group name to name table
                 70h unlink from IBM remote program (no F0h function)
                 71h send data without ACK
                 72h send multiple buffers without ACK
                 78h find name
                 79h token-ring protocol trace

        Format of struc name:

                 Offset Size    Description
                  00h 16 BYTEs nm_name
                  10h   BYTE  nm_num
                  11h   BYTE  nm_status

        Format of structure astatus:

                  00h  6 BYTEs as_id
                  06h   BYTE  as_jumpers
                  07h   BYTE  as_post
                  08h   BYTE  as_major
                  09h   BYTE  as_minor
                  0Ah   WORD  as_interval
                  0Ch   WORD  as_crcerr
                  0Eh   WORD  as_algerr
                  10h   WORD  as_colerr
                  12h   WORD  as_abterr
                  14h   DWORD as_tcount
                  18h   DWORD as_rcount
                  1Ch   WORD  as_retran
                  1Eh   WORD  as_xresrc
                  20h  8 BYTEs as_res0
                  28h   WORD  as_ncbfree
                  2Ah   WORD  as_ncbmax
                  2Ch   WORD  as_ncbx
                  2Eh  4 BYTEs as_res1
                  32h   WORD  as_sespend
                  34h   WORD  as_msp
                  36h   WORD  as_sesmax
                  38h   WORD  as_bufsize
                  3Ah   WORD  as_names
                  3Ch 16 name structures  as_name

        Note: Sytek PCnet card uses DMA 3.