Int 61 Fn 1F  - PC/tcp Kernel V2.05+ - "net_asynch" - Set Up Asynchronous  [N]

   AH = 1Fh
   BX = network descriptor
   CX = event type (see below)
   DS:SI -> event handler routine
   ES:DI = 32-bit hint passed to handler

Return: CF clear if successful
       DS:DX -> previous handler
   CF set on error
       AX = error code (see INT 61"PC/TCP")

Note:  ICMP messages do not trigger events on stream connections

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

Values for event type:
 00h   alarm
 01h   open (successfully opened stream connection)
 02h   receive (data available)
 03h   transmit (ACK received on stream connection)
 04h   transmit flush???
 05h   foreign close (remote host closed data connection)
 06h   close (local host closed connection and protocol is complete)
 07h   error (error code passed to handler as arg)

Event handler called with:
   BX = network descriptor
   CX = event type (see above)
   DS:DX -> arg
   ES:DI = 32-bit hint value
   STACK:  small stack, possibly the DOS stack