pckt(7) 						 Miscellaneous Information Manual						   pckt(7)

NAME

       pckt - STREAMS module for constructing message packets on a pty

DESCRIPTION

       The pckt module is a STREAMS module that can be used with a pseudoterminal to transfer messages in packet mode.	The packet mode feature of
       pty devices allows the user process on the master side of the device to be informed of state changes.

       For packet mode to be enabled in the pty device, the user process must push the pckt module onto the master side of the pty with a call	to
       the STREAMS I_PUSH ioctl() function.

       When  the  user	process  writes data, the pckt module passes the message on to the next module or driver unchanged.  When the user process
       reads data or when the pckt module receives certain STREAMS message types, it constructs  a  packet  out  of  the  message  for	forwarding
       upstream.

       To construct a message packet, the module creates an M_PROTO message.  This M_PROTO message contains the original message type in the first
       data block and the original message in as many data blocks as needed.  The user process can then retrieve the M_PROTO message with  a  call
       to the getmsg() function.

       The  STREAMS  message types that the pckt module places in packets, are the following:	   M_DATA      M_IOCTL	    M_PROTO	 M_PCPROTO
	    M_FLUSH	 M_START      M_STOP	  M_STARTI	M_STOPI      M_READ

       All other messages are passed unchanged upstream.

       If the message is an M_FLUSH message, the pckt module looks at the flag and takes the following actions: If the flag is FLUSHW, the  module
       changes	it  to FLUSHR before creating the M_PROTO message, and passes the message upstream.  The module also sends an M_FLUSH message with
       the FLUSHW flag set.  If the flag is FLUSHR, the module changes it to FLUSHW before creating the M_PROTO message, and  passes  the  message
       upstream.   If  the  flag is FLUSHRW, the module changes it to FLUSHW before creating the M_PROTO message, and passes the message upstream.
       The module also sends an M_FLUSH message with the FLUSHW flag set.

RELATED INFORMATION

       Functions: getmsg(2), ioctl(2).	Interfaces: ldterm(7), ptem(7), streamio(7).  delim off

																	   pckt(7)