connld(7)                        UNIX System V                        connld(7)


NAME
      connld - line discipline for unique stream connections

DESCRIPTION
      connld is a STREAMS-based module that provides unique connections between
      server and client processes.  It can only be pushed [see streamio(7)]
      onto one end of a STREAMS-based pipe that may subsequently be attached to
      a name in the file system name space.  After the pipe end is attached, a
      new pipe is created internally when an originating process attempts to
      open(2) or creat(2) the file system name.  A file descriptor for one end
      of the new pipe is packaged into a message identical to that for the
      ioctl ISENDFD [see streamio(7)] and is transmitted along the stream to
      the server process on the other end.  The originating process is blocked
      until the server responds.

      The server responds to the ISENDFD request by accepting the file
      descriptor through the IRECVFD ioctl message.  When this happens, the
      file descriptor associated with the other end of the new pipe is
      transmitted to the originating process as the file descriptor returned
      from open(2) or creat(2).

      If the server does not respond to the ISENDFD request, the stream that
      the connld module is pushed on becomes uni-directional because the server
      will not be able to retrieve any data off the stream until the IRECVFD
      request is issued.  If the server process exits before issuing the
      IRECVFD request, the open(2) or the creat(2) system calls will fail and
      return -1 to the originating process.

      When the connld module is pushed onto a pipe, messages going back and
      forth through the pipe are ignored by connld.

      On success, an open of connld returns 0.  On failure, errno is set to the
      following values:

      EINVAL       A stream onto which connld is being pushed is not a pipe or
                   the pipe does not have a write queue pointer pointing to a
                   stream head read queue.

      EINVAL       The other end of the pipe onto which connld is being pushed
                   is linked under a multiplexor.

      EPIPE        connld is being pushed onto a pipe end whose other end is no
                   longer there.

      ENOMEM       An internal pipe could not be created.

      ENXIO        An MHANGUP message is at the stream head of the pipe onto
                   which connld is being pushed.

      EAGAIN       Internal data structures could not be allocated.




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connld(7)                        UNIX System V                        connld(7)


      ENFILE       A file table entry could not be allocated.

SEE ALSO
      streamio(7)
      Programmer's Guide: STREAMS

















































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