I've only begun with blockchain(rinkeby-testnet) and IOT. I use nodemcu (ARDUINO IDE) and mist. What should the rpc-ip address be? Do I have to establish an ethereum node in order to do that ?
I think you are right.
API AND CONSOLE OPTIONS:
--rpc Enable the HTTP-RPC server
--rpcaddr value HTTP-RPC server listening interface (default: "localhost")
--rpcport value HTTP-RPC server listening port (default: 8545)
--rpcapi value API's offered over the HTTP-RPC interface