connld(7)                        DG/UX R4.11                       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.

       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.

       ENFILE       A file table entry could not be allocated.

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


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