INT 14 - Connection Manager - RETURN COMMUNICATION PORT STATUS
        AH = 03h
        DX = FFFFh
        AL = connection ID
Return: AH = return code (00h-02h) (see AH=00h/DX=FFFFh)
        BH = line status (see below)
        BL = modem status (see AH=03h above) (only bits 4,5,7; all others zero)
Notes:  if DX is 0-3 on entry, Connection Manager emulates the standard BIOS
          function, but redirects the port over the network; if DX is any other
          value, the call is chained
SeeAlso: AH=00h/DX=FFFFh,AH=04h/DX=FFFFh,AH=0Ah/DX=FFFFh

Bitfields for line status:
 bit 7  CTS changed
 bit 6  current CTS state
 bit 5  timeout
 bit 4  break
 bit 3  framing error
 bit 2  parity error
 bit 1  overrun
 bit 0  current carrier state (0 active, 1 no carrier)

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