Can I suggest updated sourceforge to say that the code has been moved to github, and leaving little else there? That way it's easier to update everything in the same place. I was browsing on sourceforge for a while and wondering "Why isn't this on github instead?" It wasn't even until I came back and started skimming this thread that I realized it was moved to github.
I got a test circuit wired up yesterday afternoon with one temperature sensor and the arduino. It didn't work. I got out the multimeter and there was not voltage coming through the wire connected (through the breadboard) to the VCC contact in the arduino, even though there was voltage if I touched it to the arduino contact directly. Apparently something I'm doing with the headers is not quite right. I'll research and try to figure it out, but I'd be happy if anybody here has suggestions.
Ok, now we're cooking! @tekka, thanks for explaining some of the details that I was missing. I'm sure I read that before, but I guess I swapped "gateway" with "controller" in my head, assuming that the sensor node would be assigned an id by the gateway.
I placed the following in my sensor node's sketch:
#define MY_NODE_ID 2
This avoided any errors, but I still wasn't seeing the correct message come through MQTT.
Not sure if it was required, but I ended up having to add
#define MY_PARENT_NODE_ID 1
to the sensor node's sketch, and
#define MY_NODE_ID 1
to the gateway node's sketch. Once I did that, the temperature readings started showing up in MQTT!
Thanks for the help everybody. I still have quite a bit to learn, but getting a working sensor sending data all the way through the gateway to MQTT was the biggest hurdle to really making progress on implementing these. THANK YOU!