Int 61 Fn 1B  - PC/tcp Kernel V2.05+ - "net_read" - Read From The Network  [N]

   AH = 1Bh
   BX = network descriptor
   CX = maximum number of bytes to read
   DX = receive options (see below)
   DS:SI -> buffer for data
   ES:DI -> "addr" structure (see AH=13h) for remote from which to read
       0000h:0000h for any

Return: CF clear if successful
       AX = number of bytes actually read
       DX = ???
   CF set on error
       AX = error code (see INT 61"PC/TCP")

See Also: INT 61"PC/TCP",INT 61/AH=00h"PC/TCP",INT 61/AH=1Ah,INT 61/AH=1Dh

Bitfields for receive options:
 bit 1 do not remove data from queue, just copy it
 bit 2 do not copy data, just remove it from queue
 bit 5 fail if datagram would be truncated
 bit 6 do not block, return error if no data available

Note:  special case for UDP: if both bits 1 and 2 set, return num of datagrams