ardunio rpc websockets ...

 https://randomnerdtutorials.com/esp32-web-server-websocket-sliders/
ESP32 Web Server (WebSocket) with Multiple Sliders: Control LEDs Brightness (PWM)

https://os.mbed.com/cookbook/RPC-over-Websockets

https://github.com/elpheria/rpc-websockets

https://www.youtube.com/watch?v=LtTWSq93MTo
RPC LED Control with Sliders over Websockets

A Beginner's Guide to the ESP8266
https://tttapa.github.io/ESP8266/Chap14%20-%20WebSocket.html

https://diyprojects.io/websocket-communication-esp8266-arduino-python-test-ws4py-library-raspberry-pi/#.YNy3VjpOlFQ

https://blog.thingsboard.io/2017/01/esp8266-gpio-control-over-mqtt-using.html?m=0

Remote Procedure Calls (RPC)
https://www.youtube.com/watch?v=QmhTjsOOrlw

(edit aug 22: add this link: https://www.youtube.com/watch?v=S2osKiqQG9s )

Sending JSON over WebSockets - JavaScript Tutorial
https://www.youtube.com/watch?v=JxdPunrO084

Issues in RPC & How They're Resolved
https://www.youtube.com/watch?v=jH3RezOHROU

Simple RPC implementation for Arduino.
https://simplerpc.readthedocs.io/en/latest/
https://simplerpc.readthedocs.io/en/latest/introduction.html
https://arduino-simple-rpc.readthedocs.io/en/latest/#quick-start

https://github.com/jfjlaros/simpleRPC

https://arduino-simple-rpc.readthedocs.io/en/latest/usage.html

 

Or Weis: Python RPC and PubSub over Websockets
https://www.youtube.com/watch?v=KP7tPeKhT3o

https://www.jsonrpc.org/specification

https://eips.ethereum.org/EIPS/eip-2844


REST vs RPC vs GraphQL API - How do I pick the right API paradigm?
https://www.youtube.com/watch?v=hkXzsB8D_mo

Nate Barbettini – API Throwdown: RPC vs REST vs GraphQL, Iterate 2018
https://www.youtube.com/watch?v=IvsANO0qZEg

Ethereum, The Graph, React, and all that...

I've done some preliminary research:

Query Ethereum with GraphQL with The Graph 
https://www.youtube.com/watch?v=l2rzT_Dp4T0 (shows how to use the graph with node and react)

Nader Dabit's The Graph Presentations:
https://www.youtube.com/watch?v=wrV7cMebwyE , https://www.youtube.com/watch?v=wrV7cMebwyE

ETHOnline 🛠️ The Graph: Building Subgraphs on The Graph
https://www.youtube.com/watch?v=coa0Vw47qNc
https://reactjs.org/tutorial/tutorial.html

I'm trying to build an application using the graph and react. I'm new to both, but at least I've learned something. 

Drawing from (forked repositories): 
https://github.com/bshambaugh/example-subgraph
https://github.com/bshambaugh/ethdenver-dapp 
https://github.com/bshambaugh/building-a-subgraph-workshop


This is also an interesting place to look:

Getting Started With React And GraphQL

https://www.youtube.com/watch?v=5evJqX5i1zE

Analog to Digital Converter useful for the Rasperry Pi

 #104 ADS1115 Analog-to-Digital Converter for Arduino, Pi 🥧& All (2018)
https://www.youtube.com/watch?v=8qGr6Q5Ymps

TUTORIAL: How to / About the ADS1115 External 16 Bit ADC - Part 2
https://www.youtube.com/watch?v=XxUMc1jnI9U

TUTORIAL: How to / About the ADS1115 External 16 Bit ADC - Part 1
https://www.youtube.com/watch?v=oQ2lz2ZckRQ

Arduino, ADS1115 16-Bit ADC with I2C Bus and Adafruit Library – The Details
https://www.youtube.com/watch?v=7iL94z5XRFA