Note that jwatte built his own system around ZMQ (mostly UDP) and RPCs because he couldn't figure out ROS (and also did not want to have to install Ubuntu just for installing ROS successfully). I had been working on a comprehensive motion control system for arbitrary robot designs built around ZMQ with stochastic gait seeking modules/nodes, but mostly gave up a couple years back. The somewhat higher performance of ZMQ was simply not necessary and the amount of work to get the ZMQ system up and running was in no way worth the effort compared to just using ROS for all the inter-node communications.