Function establish 

pub async fn establish(
    read_half: BoxRead,
    write_half: BoxWrite,
    key: &NodeKey,
    role: Role,
    client_id: &str,
    listen_port: u16,
) -> Result<Established, EstablishError>

The RLPx handshake, then Hello both ways. Our Hello goes out first and unconditionally — it is NetGet’s identity, not a decision — and the peer’s must name the key it authenticated with and share an eth version.