Talking to devices without discovery

[wz2b]

I have a bunch of devices I want to talk to occasionally that's behind a firewall. Messages to/from port 47808 pass fine, but broadcasts do not work.

The device is a Wattstopper digital lighting control segment manager that sits on ethernet. Behind it are four MS/TP segments.

I figured out that I can do the following:

 int instanceNumber = 1234;   /* not the real instance id of the gateway/segment manager */
Address segmentManagerAddress = new Address("10.1.2.3", 47808);  /* not the real IP address */
OctetString segmentManagerLinkService = null;
RemoteDevice segmentManager = new RemoteDevice(instanceNumber, segmentManagerAddress, segmentManagerLinkService);
segmentManager.setSegmentationSupported(Segmentation.noSegmentation);
segmentManager.setMaxAPDULengthAccepted(1476);
Encodable descr = RequestUtils.sendReadPropertyAllowNull(localDevice,
                segmentManager,
                remoteRequestOid,
                PropertyIdentifier.description);

this gets me a description so it works.

My next step is to figure out how to talk to the devices that are on the networks BEYOND the gateway/segment manager. Each one has its own network ID and a bunch of devices.

Without using broadcast discovery, how do I configure a RemoteDevice that can talk to these devices?

[Frozenlock]

Perhaps you could send the WhoIs directly to the device instead of using a broadcast?

On a semi-related note, you are communicating with a remote device behind a firewall...
Does it mean you exposed the port 47808 to the Internet? :shock:

[wz2b]

Not in my case, but I have noticed that a lot of folks aren't particularly careful about this. I find it very troubling.

Perhaps you could send the WhoIs directly to the device instead of using a broadcast?

Yeah. That lets me see interesting things about the gateway ... but I haven't figured out how to make it tell me about ("discover") things BEYOND the gateway. If I known the network #, device ID, and MAC of the MS/TP device (as an example) then I can talk to it. I feel like this is fragile, though - like what if the power recycles and all these devices come up and arbitrate for new MAC addresses? How do I prevent my software from getting confused by this?

[Frozenlock]

Glad to hear you don't expose your BACnet port!

I'm a little rusty on the discovery process.
When answering a WhoIs, isn't the gateway supposed to send you the list of devices it knows about?

As a patch, perhaps you could 'scan' for these devices every once in a while to make sure you have all of them.
Say all device from ID 0 to 99 (or whatever is their ID range).