message_connect()

Create a connection to a channel

Synopsis:

#include <sys/iofunc.h>
#include <sys/dispatch.h>

int message_connect( dispatch_t * dpp,
                     int flags );

Arguments:

dpp

The dispatch handle, as returned by dispatch_create().

flags

Currently, the following flag is defined in <sys/dispatch.h>:

• MSG_FLAG_SIDE_CHANNEL — request the connection ID be returned from a different space. This ID will be greater than any valid file descriptor. Once created there's no difference in the use of the messaging primitives on these IDs.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The message_connect() function creates a connection to the channel used by dispatch handle dpp. This function calls the ConnectAttach() kernel call. To detach the connection ID, you can call ConnectDetach().

---

The message_connect() function works only when the dispatch blocking type is receive, i.e. attaches were done for resmgr, message, or select “type” events. If no attaches were done yet, the message_connect() call fails, since dispatch can't determine if receive or sigwait blocking will be used.

---

Returns:

A connection ID used by the message primitives, or -1 if an error occurs (errno is set).

Errors:

EAGAIN

All kernel connection objects are in use.

EINVAL

Dispatch dpp doesn't have a channel.

Examples:

#include <sys/dispatch.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
        
int main( int argc, char **argv ) {
   dispatch_t    *dpp;
   int           flags, coid, id;
    
   if( ( dpp = dispatch_create() ) == NULL ) {
     fprintf( stderr, 
        "%s: Unable to allocate dispatch context.\n",
        argv[0] );
     return EXIT_FAILURE;
   }

   id = resmgr_attach ( … );
    
   …

   if ( (coid = message_connect ( dpp, flags )) == -1 ) {
      fprintf ( stderr, "Failed to create connection \
                to channel used by dispatch.\n");
      return 1;
   }
   /* else connection to channel used by dispatch is created */
            
   …
}

For examples using the dispatch interface, see dispatch_create(), message_attach(), resmgr_attach(), and thread_pool_create().

Classification:

QNX Neutrino

Caveats:

Dispatch dpp must block on messages.

See also:

ConnectAttach(), message_attach()

“Layers in a resource manager” in the Bones of a Resource Manager chapter of Writing a Resource Manager