On 03/26/2012 06:14 PM, Doug Brunner wrote:
Thanks for the information--the issue is not about picking a free port on the server
side, but rather about communicating the information on which ports are "free"
to the clients (server has connected its end, but no other client is using the port). The
semaphore mechanism isn't that much of a problem, though; I've been able to build a
satisfactory implementation.
Mm, still scratching my head to understand the issue. Both the client
and server side accept -1 as the port spec, telling the kernel to draw a
free port. I understand the issue is not on the server side, so is it on
the client side?
Could you sketch the usage pattern?
One other question: although I know in-order delivery isn't necessarily a
feature of datagram based protocols, would I get that with an IDDP socket
connection between just two processes, and/or an XDDP connection to a /dev/rtpN?
Yes, in-order delivery is guaranteed with all RTIPC protocols. This is
written in stone.
Doug Brunner
-----Original Message-----
From: "Philippe Gerum"<[email protected]>
Sent: Friday, March 16, 2012 11:29am
To: "Doug Brunner"<[email protected]>
Cc: [email protected]
Subject: Re: [Xenomai-help] Intermixing native and POSIX skins
On 03/15/2012 05:30 PM, Doug Brunner wrote:
Thanks Philippe. I hadn't even known about the existence of the RTIPC driver,
and I definitely like the idea.
I've been experimenting with it a bit today, and found that it seems to be
allowed for more than two sockets to connect to the same port. I modified
iddp-sendrecv.c to have two client processes, both of which now connect to the
same port as the server, then did the same thing with iddp-label.c (two clients
both connect()ing to the same label).
This would cause havoc with the communications that go on between my
processes--they need a one-to-one channel. I could implement semaphores to
enforce this, but it would be nice to avoid that complication. Is there a way
to make it happen using just the socket interface?
The RTIPC protocols are fundamentally datagram-based, so allowing N:1
data paths is wanted. If the issue is about picking a different port
each time you bind a server socket in the AF_RTIPC domain, then I would
suggest to set sipc_port to -1 when binding the server-side socket: a
free port will be picked automatically. You could then use getsockname()
to retrieve the actual port #, and pass it to the clients.
--
Philippe.
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