Net Bios Control Block (NCB) Format
┌─────┬─────┬──────────┬───────────────────────────────────────────┐
│Off- │Size │ Field │ Field │
│set │Bytes│ Name │ Description │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 00h │ 1 │ Command │ Net Bios command code. High order bit │
│ │ │ │ set indicates no-wait mode. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 01h │ 1 │ RetCode │ Completion result. Zero if no error. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 02h │ 1 │ LSN │ Local session number (1 to 254). Returned │
│ │ │ │ by CALL and LISTEN, and supplied for │
│ │ │ │ SEND and RECEIVE commands. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 03h │ 1 │ Num │ Name Number (1 to 254). Returned by ADD │
│ │ │ │ NAME commands, and supplied for RECEIVE │
│ │ │ │ ANY and datagram commands. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 04h │ 4 │ BufAdr │ Address of message for send and receive. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 08h │ 2 │ BufLen │ Length of message buffer. For receive │
│ │ │ │ commands, supply the maximum buffer size │
│ │ │ │ and the actual length is returned. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 0Ah │ 16 │ CallName │ Name from/of remote machine for CALL, │
│ │ │ │ LISTEN and datagrams. For a CHAIN SEND │
│ │ │ │ command, the first word specifies the │
│ │ │ │ length of the second buffer, and the │
│ │ │ │ next two words specify the address. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 1Ah │ 16 │ Name │ Local name. Specifies name to add for ADD │
│ │ │ │ NAME, or name to use for other commands. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 2Ah │ 1 │ RTO │ Receive time-out in .5 second increments. │
│ │ │ │ Supplied on CALL and LISTEN commands. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 2Bh │ 1 │ STO │ Send time-out in .5 second increments. │
│ │ │ │ Supplied on CALL and LISTEN commands. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 2Ch │ 4 │ Post │ Address of user interrupt routine called │
│ │ │ │ when command completes and no-wait mode │
│ │ │ │ mode was specified in command code. Not │
│ │ │ │ called if set to 0:0. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 30h │ 1 │ LANA_Num │ Number of adapter card -- 0 for the first │
│ │ │ │ and 1 for the second, if applicable. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 31h │ 1 │ CMD_Done │ Command completed flag. A value of 0FFH │
│ │ │ │ indicates the command has not completed. │
│ │ │ │ When the command has completed, CMD_DONE │
│ │ │ │ is set to same value as RETCODE. │
├─────┼─────┼──────────┼───────────────────────────────────────────┤
│ 32h │ 14 │ Reserved │ Used internally by Net Bios. │
└─────┴─────┴──────────┴───────────────────────────────────────────┛