Rocket League is often cited as a complex game netcode-wise, mainly because it's hard to get networked physics to play nicely over latency. This is why I chose to try recreate the core of the game as a learning sample for my networking solution (Netick).
The project shows how to do predicted physics that behave nicely even at high ping, goal replay, full-match replay (using Netick's built-in replay feature), in-game text chat, and more.
We are releasing the sample project alongside Netick 2 asset store release. We have been developing Netick 2 for years, where, even during beta, it was used in several commercial projects. Rocket Cars serves as our production-ready sample for new users.
The project is open source (MIT License): https://github.com/NetickNetworking/NetickRocketCars