I initially tried sending params to the talker without adding any code, and it failed. So that puts this statement into question.
Thanks for the insight on the proper usage.
I guess I never knew this. What is the API for setting/getting params in Node? I hadn’t seen anything in the past. Maybe things have changed and I’m just oblivious. 
The way I’ve been working with parameters is to create a Service and Client for each node. Then I register an event callback for each node. And inside the param event callback for each node, I condition on the name of the parameter being modified/created/deleted, and assign the value to a local variable used for computation, etc.
Sounds like that approach is off-the-mark. I’ll look into the Node::register_param_change_callback() method and modify how I’m working with parameters.
Usually my use case is to create/setup my node, wait for parameters to be set to a good value (typically by an external entity), then proceed to do work.