Hi Paul:

	This doesn't sound like it's supported in our stack.  There are
a few ways that I could see this working.  Having the driver listening
while it transmits (i.e. wholly in hardware), having the driver
recognize a broadcast packet and send it back up the stack in addition
to transmitting it and finally having the stack somehow loop back
certain packets before they hit the driver.  The stack option seems very
difficult to manage, so I'd guess that it would be something in the
driver or hardware.  Our drivers (and I would have thought most
hardware) don't support a "listen to what I transmit" scenario.

Do you have to do something special to Windows to make this happen or is
it a default behaviour?

	Robet.

-----Original Message-----
From: Paul Kahn [mailto:community-noreply@qnx.com] 
Sent: Tuesday, December 16, 2008 3:52 PM
To: technology-networking
Subject: Re: RE: Sending and receiving broadcast messages via the same
interface

Hi Robert,

The final network topology will be a little complicated. However, for
purposes of discussion, let's assume the following: 

The subnet is 10.0.0.0 with subnet mask of 255.255.255.0. There are two
boards running QNX on this subnet. Each of the two boards has one
Ethernet interface one with address 10.0.0.100 and the other with
address 10.0.0.200. Our software will communicate using a proprietary
protocol over UDP.

We are able to send broadcast messages from one board to another.
However they are on separate boards and have different IP addresses.
We'd also like to be able to receive broadcast messages sent from the
same board. Ideally, we'd like to be able to send a broadcast out from
10.0.0.100:4000 and receive it via a socket bound to that address
(actually the same socket). Alternatively we'd be happy to receive a
broadcast message sent from 10.0.0.100:4000 and receive it via a
different socket bound to 10.0.0.100:4001. 

However, it appears we cannot receive broadcast messages from the same
Ethernet interface. Hence my question about the simplex flag which
appears to be set for "en0".

Our code runs on both QNX and Windows and this works on Windows.
However, I realize that the network stacks and even the sockets
implementations are vastly different. 

Thanks,
--Paul


_______________________________________________
Technology
http://community.qnx.com/sf/go/post18766

As a side note, we can check into the stack implementation to verify
this.  Which stack are you using (io-net or io-pkt)?

	Robert. 

-----Original Message-----
From: Robert Craig 
Sent: Tuesday, December 16, 2008 4:10 PM
To: 'post18766@community.qnx.com'
Subject: RE: RE: Sending and receiving broadcast messages via the same
interface

Hi Paul:

	This doesn't sound like it's supported in our stack.  There are
a few ways that I could see this working.  Having the driver listening
while it transmits (i.e. wholly in hardware), having the driver
recognize a broadcast packet and send it back up the stack in addition
to transmitting it and finally having the stack somehow loop back
certain packets before they hit the driver.  The stack option seems very
difficult to manage, so I'd guess that it would be something in the
driver or hardware.  Our drivers (and I would have thought most
hardware) don't support a "listen to what I transmit" scenario.

Do you have to do something special to Windows to make this happen or is
it a default behaviour?

	Robet.

-----Original Message-----
From: Paul Kahn [mailto:community-noreply@qnx.com]
Sent: Tuesday, December 16, 2008 3:52 PM
To: technology-networking
Subject: Re: RE: Sending and receiving broadcast messages via the same
interface

Hi Robert,

The final network topology will be a little complicated. However, for
purposes of discussion, let's assume the following: 

The subnet is 10.0.0.0 with subnet mask of 255.255.255.0. There are two
boards running QNX on this subnet. Each of the two boards has one
Ethernet interface one with address 10.0.0.100 and the other with
address 10.0.0.200. Our software will communicate using a proprietary
protocol over UDP.

We are able to send broadcast messages from one board to another.
However they are on separate boards and have different IP addresses.
We'd also like to be able to receive broadcast messages sent from the
same board. Ideally, we'd like to be able to send a broadcast out from
10.0.0.100:4000 and receive it via a socket bound to that address
(actually the same socket). Alternatively we'd be happy to receive a
broadcast message sent from 10.0.0.100:4000 and receive it via a
different socket bound to 10.0.0.100:4001. 

However, it appears we cannot receive broadcast messages from the same
Ethernet interface. Hence my question about the simplex flag which
appears to be set for "en0".

Our code runs on both QNX and Windows and this works on Windows.
However, I realize that the network stacks and even the sockets
implementations are vastly different. 

Thanks,
--Paul


_______________________________________________
Technology
http://community.qnx.com/sf/go/post18766

On Tue, Dec 16, 2008 at 03:51:45PM -0500, Paul Kahn wrote:
> Hi Robert,
> 
> The final network topology will be a little complicated. However, for purposes of discussion, let's assume the 
following: 
> 
> The subnet is 10.0.0.0 with subnet mask of 255.255.255.0. There are two boards running QNX on this subnet. Each of the
 two boards has one Ethernet interface one with address 10.0.0.100 and the other with address 10.0.0.200. Our software 
will communicate using a proprietary protocol over UDP.
> 
> We are able to send broadcast messages from one board to another. However they are on separate boards and have 
different IP addresses. We'd also like to be able to receive broadcast messages sent from the same board. Ideally, we'd 
like to be able to send a broadcast out from 10.0.0.100:4000 and receive it via a socket bound to that address (actually
 the same socket). Alternatively we'd be happy to receive a broadcast message sent from 10.0.0.100:4000 and receive it 
via a different socket bound to 10.0.0.100:4001. 
> 
> However, it appears we cannot receive broadcast messages from the same Ethernet interface. Hence my question about the
 simplex flag which appears to be set for "en0".
> 
> Our code runs on both QNX and Windows and this works on Windows. However, I realize that the network stacks and even 
the sockets implementations are vastly different. 
> 

We do loop a copy of broadcast packets sent on ethernet back
on loopback.  If you can receive any broadcast packets you
should also get the ones you send.  You can check the 'netstat -in'
counts to see if the localhost counts increase on receive.
'netstat -pudp' has a dropped broadcast count as well.

-seanb