Run

grpc_tools_node_protoc --js_out=import_style=commonjs,binary:. --grpc_out=grpc_js:. todo.proto

python -m grpc_tools.protoc -I . --python_out=. --grpc_python_out=. ./todo.proto

then run in a terminal

python server.py

and in another terminal

node client.js --todo <todotext>