For questons about RLPx, a cryptographic peer-to-peer network and protocol suite which provides a general-purpose transport and interface for applications to communicate via a p2p network.

From https://github.com/ethereum/devp2p/blob/master/rlpx.md

RLPx is a cryptographic peer-to-peer network and protocol suite which provides a general-purpose transport and interface for applications to communicate via a p2p network. RLPx is designed to meet the requirements of decentralized applications and is used by Ethereum.