Path: utzoo!attcan!uunet!bloom-beacon!apple!zorba!dtynan
From: raghu@timbaktu.osc.edu (Raghu)
Newsgroups: comp.unix
Subject: Message queues
Keywords: Problem in usage, Performance
Message-ID: <3483@zorba.Tynan.COM>
Date: 7 Oct 89 22:59:23 GMT
Sender: dtynan@zorba.Tynan.COM
Lines: 30
Approved: dtynan@zorba.Tynan.COM

Two questions about message queues in UNIX:

1. I have a problem withe following piece of code.  I am trying to use the
message queue facility in UNIX and I have come across a strange problem.
The constant KERNEL_PORT is 2401 and the getuid call returns 104 (my uid on
our SUNS).  Then, with a key of 2505 the call msgget blow out with the
message "Permission Denied".  That should not happen as I set the msgflag to
reflect that (0000600).  Has anyone else seen this problem or aware of this
problem...


/*	if ((myqid = msgget((key_t) (KERNEL_PORT + getuid()), IPC_CREAT|0000600))	*/
	if ((myqid = msgget((key_t) getuid(),IPC_CREAT|0000600))
			== ERROR) {			
		perror("kernel (msgget)");
		exit(errno);
	}


2. I am exploring the use of message queues instead of the traditional
socket IPC operations.  The application involves a daemon-like program to
rendezvous two other processes and I want to use the message queue facility
to make synchronization possible.  I am interesting in evaluating on how
much faster it would be to go this way.  Gut feeling indicates that message
queues could be faster than passing UDP packets around and this might be
because the UNIX kernel supports this facility better (and probably uses it).  

Any ideas or comments !!

Raghu