plan9 man page for flush

FLUSH(5)							File Formats Manual							  FLUSH(5)

NAME
       flush - abort a message

SYNOPSIS
       Tflush  tag[2] oldtag[2]
       Rflush  tag[2]

DESCRIPTION
       When  the  response to a request is no longer needed, such as when a user interrupts a process doing a read(2), a Tflush request is sent to
       the server to purge the pending response.  The message being flushed is identified by oldtag.  The semantics of flush depends  on  messages
       arriving in order.

       The  server  must  answer  the flush message immediately.  If it recognizes oldtag as the tag of a pending transaction, it should abort any
       pending response and discard that tag.  In either case, it should respond with an Rflush echoing the tag (not oldtag) of  the  Tflush  mes-
       sage.  A Tflush can never be responded to by an Rerror message.

       When  the client sends the Tflush, it should disregard all messages received with tag oldtag until the corresponding Rflush is received, at
       which point oldtag may be recycled for subsequent messages.

       Several exceptional conditions are handled correctly by the above specification: sending multiple flushes for  a  single  tag,  flushing  a
       Tflush, and flushing an invalid tag.

																	  FLUSH(5)