Re: [Bacnet-developers] DNET and gateway

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Hello Derek Noffke,

The command line apps allow for usage of BACNET_IFACE environment variable
which you can set to the interface returned by ifconfig (on Linux) or the
IP address (on Windows).  If you set (export) BACNET_IFACE to the
appropriate interface, the initialization code will lookup the broadcast
address appropriate for the interface.

As Dave mentioned BBMD is used to share broadcast messages which often are
not routed from subnet to subnet. The BACnet/IP solution is to unicast the
broadcast to a BBMD in another subnet where it can broadcast it locally.
The dlenv.c module is used by most of the example command line apps to read
some OS environment variables and configure the example app for the site.
There are likely (at least in later versions) environment variables to
configure the BBMD entries for the command line applications.

Best regards,

Steve

On Fri, May 21, 2021 at 7:42 AM Derek Noffke <de...@pu...> wrote:

> Making some slowgress.
>
> 1)      I had compiled the gateway to use who-is unicast
> //apdu_set_unconfirmed_handler(SERVICE_UNCONFIRMED_WHO_IS,
> handler_who_is_unicast);
> apdu_set_unconfirmed_handler(SERVICE_UNCONFIRMED_WHO_IS, handler_who_is);
>
> 2)      The broadcast goes to 255.255.255.255
> Seems the bip_init() is only called once??? and expects the ifname “eth0”
> If a who-is arrives on eth1 then the broadcast mask from eth0 is used.
>
> Am I missing anything here?
>
>
>
>
>
>
>
>
>
> Regards,
>
>
>
> Derek Noffke
>
> PurpleSwift
>
> Cell: 082 780 4680
>
> Tel: 021 761 8264
>
>
>
>
>
>
>
> *From:* Derek Noffke [mailto:de...@pu...]
> *Sent:* Wednesday, 19 May 2021 18:28
> *To:* 'Discussion for developers of the BACnet stack'
> *Subject:* Re: [Bacnet-developers] DNET and gateway
>
>
>
> I am still trying to solve this issue.
>
> I have installed tshark on my linux device so at least I can see the
> bacnet traffic.
>
>
>
> The setup is as follows:
>
> PC with BACnet client software at IP 155.247.120.90
>
> PC is registered as a foreign device on BBMD at IP 10.124.44.63
>
> My device 2700000 is at IP 10.124.44.94
>
> Just to make things a little more difficult the subnet mask is 22 bits  L
>
>
>
> [image: 3352 2021-05-19 12:10:51,278265 10.124.44.63 10.124.47.255
> BACnet-APDU 60 47814 Unconfirmed-REQ who-Is 3353 2021-05-19 12:10:51,278544
> 10.124.44.57 10.124.47.255 BACnet-APDU 68 47814 Unconfirmed-REQ i-Am
> device,1045010 3354 2021-05-19 12:10:51,278605 10.124.44.94 155.247.120.90
> BACnet-APDU 63 51948 Unconfirmed-REQ i-Am device,2700000]
>
>
>
>
>
>
>
>
>
>
>
> So the PC sends a broadcast who-is to the BBMD on port 51948
>
> The BBMD resends the who-is shown on line 3352 on port 47814
>
> Some other bacnet device responds with a broadcast i-am on line 3353 on
> port 47814
>
> My device sends a unicast i-am direct back to the PC on port 51948
>
>
>
> Given that the PC only sees the “other” device I assume the unicast
> message is blocked.
>
>
>
> Any help please.
>
>
>
>
>
> Regards,
>
>
>
> Derek Noffke
>
> PurpleSwift
>
> Cell: 082 780 4680
>
> Tel: 021 761 8264
>
>
>
>
>
>
>
> *From:* Dave Lindauer via BACnet-developers [mailto:
> bac...@li...]
> *Sent:* Thursday, 13 May 2021 18:49
> *To:* Derek Noffke; 'Discussion for developers of the BACnet stack'
> *Cc:* Dave Lindauer
> *Subject:* Re: [Bacnet-developers] DNET and gateway
>
>
>
> Hi Derek,
>
>
>
> Take me with a grain of salt…   I know quite a bit about bacnet over IP
> but haven’t spent extensive time setting up systems…
>
>
>
> I suppose you set it up that way presuming the BBMD is on your current
> subnet.   Then you wouldn’t need to explicitly handle BBMDs I suppose.
>
>
>
> But you are using multiple device objects routed at the same IP?   With
> the root device being DNET 0 and the rest of them being DNET 2809?   I
> don’t think you should program the DNET of 2809 into the BBMD.   I think
> what should be happening is you get the WHOIS broadcasts at the default
> DNET (0) and the bacnet stack does some work to make sure all the device
> objects  get it, since it is broadcast it can do that lol.    But the
> broadcasts will come in PTP as forwarded broadcast messages.
>
>
>
> And of course responses should have the appropriate SNET set.
>
>
>
> Not sure at this point if we had to make a modification to make it do
> either of those things though.   I know I modified that code, just cannot
> remember why…
>
>
>
> *From:* Derek Noffke <de...@pu...>
> *Sent:* Thursday, May 13, 2021 10:40 AM
> *To:* 'Discussion for developers of the BACnet stack' <
> bac...@li...>
> *Cc:* Dave Lindauer <da...@po...>
> *Subject:* RE: [Bacnet-developers] DNET and gateway
>
>
>
> Thanks Dave,
>
>
>
> I know very little about BBMD workings so any info is most welcome.  J
>
>
>
> Client on site manually adds my root device 2700000 to his BBMD.
>
> Discover works 20% of the time.
>
> Client says problem is 2700000 is on DNET 0 while all other are on DNET
> 2809
>
>
>
> Regards,
>
>
>
> Derek Noffke
>
> PurpleSwift
>
> Cell: 082 780 4680
>
> Tel: 021 761 8264
>
>
>
>
>
>
>
> *From:* Dave Lindauer via BACnet-developers [
> mailto:bac...@li...
> <bac...@li...>]
> *Sent:* Thursday, 13 May 2021 16:15
> *To:* Discussion for developers of the BACnet stack
> *Cc:* Dave Lindauer
> *Subject:* Re: [Bacnet-developers] DNET and gateway
>
>
>
> Generally the BBMD you want to talk to is on some other subnet.   To be
> compatible with a BBMD you have to register with it at intervals (the
> registration expires) so that you can get broadcasts from the other
> subnet.    Also in addition to broadcasting on your own network, you have
> to send your broadcasts directly to the BBMD in point to point fashion so
> that they can be received on the other network.   For example the IAM
> messages.
>
>
>
> There is specific protocol related to this, but the bacnet stack has
> helpers and so forth.    There might be an example as well.    I found it
> pretty easy not only to interact with BBMDs but to create one for testing!
>
>
>
> David
>
> *From:* Derek Noffke <de...@pu...>
> *Sent:* Thursday, May 13, 2021 8:59 AM
> *To:* bac...@li...
> *Subject:* [Bacnet-developers] DNET and gateway
>
>
>
> Greetings,
>
>
>
> I have an app based on the gateway demo code.  BACnet Stack Version 0.8.4
>
> I have been informed that my gateway is not compatible with a BBMD.
>
>
>
> The startup I-AM sequence is attached.
>
> I see that the I-AM for my “root” device 2700000 does NOT contain the DNET.
>
> Is this possibly the problem?
>
>
>
> Regards,
>
>
>
> Derek Noffke
>
> PurpleSwift
>
> Cell: 082 780 4680
>
> Tel: 021 761 8264
>
>
>
>
>
>
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