boost asio async_write:如何不交错async_write调用？

#include<boost/asio.hpp>
#include<iostream>
#include<vector>
#include<boost/bind.hpp>
#include<boost/enable_shared_from_this.hpp>

class Session : public boost::enable_shared_from_this<Session> {
public:
    Session(boost::asio::io_service& io_service)
        : socket_(io_service) {}

    boost::asio::ip::tcp::socket& socket() {
        return socket_;
    }

    void start() {
        boost::asio::async_write(socket_,
            boost::asio::buffer(data_, data_.size()),
            boost::bind(&Session::handle_write, shared_from_this(),
                boost::asio::placeholders::error,
                boost::asio::placeholders::bytes_transferred));
    }

private:
    void handle_write(const boost::system::error_code& error,
        size_t bytes_transferred) {
        if (!error) {
            // 写入下一个数据块
            start();
        }
    }

    boost::asio::ip::tcp::socket socket_;
    std::vector<char> data_ = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};
};

int main() {
    boost::asio::io_service io_service;

    boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::address::from_string("127.0.0.1"), 8080);
    boost::asio::ip::tcp::acceptor acceptor(io_service, endpoint.protocol());
    acceptor.bind(endpoint);
    acceptor.listen();

    boost::asio::ip::tcp::socket socket(io_service);
    acceptor.accept(socket);

    boost::shared_ptr<Session> session(new Session(io_service));
    session->socket() = std::move(socket);
    session->start();

    io_service.run();

    return 0;
}