code: func (sn *SimNode) ServeRPC(conn net.Conn) error {
  	handler, err := sn.node.RPCHandler()
  	if err != nil {
  		return err
  	}
  	handler.ServeCodec(rpc.NewJSONCodec(conn), rpc.OptionMethodInvocation|rpc.OptionSubscriptions)
  	return nil
  }
docs: // ServeRPC serves RPC requests over the given connection by creating an
  // in-memory client to the node's RPC server