Boost.Asio 名前解決

Boost.Asioでは、resolverというクラスを使用することにより、google.comのような名前から、IPアドレスに変換することができます。

ip::tcp::resolver resolver(io_service);

ip::tcp::resolver::query query("google.com", "http");
resolver.async_resolve(query, on_resolve);

以下サンプル

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

namespace asio = boost::asio;
namespace ip = asio::ip;

class Client {
    asio::io_service& io_service_;
    ip::tcp::resolver resolver_;

public:
    Client(asio::io_service& io_service)
        : io_service_(io_service),
          resolver_(io_service)
    {
        ip::tcp::resolver::query query("google.com", "http");
        resolver_.async_resolve(query,
            boost::bind(&Client::on_resolve, this,
                            asio::placeholders::error,
                            asio::placeholders::iterator));
    }

private:
    void on_resolve(const boost::system::error_code& error,
                    ip::tcp::resolver::iterator endpoint_iterator)
    {
        if (error) {
            std::cout << error.message() << std::endl;
        }
        else {
            ip::tcp::resolver::iterator end;
            for (; endpoint_iterator != end; ++endpoint_iterator) {
                std::cout << endpoint_iterator->endpoint().address().to_string() << std::endl;
            }
        }
    }
};

int main()
{
    asio::io_service io_service;

    Client client(io_service);

    io_service.run();
}

66.249.89.99
66.249.89.104

Boost.Asioの接続関数には名前解決されたendpoint iteratorを間接参照して渡します。

socket.async_connect(*endpoint_iterator, on_connect);

以下サンプル：

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

namespace asio = boost::asio;
namespace ip = asio::ip;

class Client {
    asio::io_service& io_service_;
    ip::tcp::resolver resolver_;
    ip::tcp::socket socket_;

public:
    Client(asio::io_service& io_service)
        : io_service_(io_service),
          resolver_(io_service),
          socket_(io_service)
    {
        ip::tcp::resolver::query query("google.com", "http");
        resolver_.async_resolve(query,
            boost::bind(&Client::on_resolve, this,
                            asio::placeholders::error,
                            asio::placeholders::iterator));
    }

private:
    void on_resolve(const boost::system::error_code& error,
                    ip::tcp::resolver::iterator endpoint_iterator)
    {
        if (error) {
            std::cout << "cannot resolve: " << error.message() << std::endl;
        }
        else {
            std::cout << "success resolve" << std::endl;
            socket_.async_connect(*endpoint_iterator,
                        boost::bind(&Client::on_connect, this, asio::placeholders::error));
        }
    }

    void on_connect(const boost::system::error_code& error)
    {
        if (error) {
            std::cout << "cannot connect: " << error.message() << std::endl;
        }
        else {
            std::cout << "success connect" << std::endl;
        }
    }
};

int main()
{
    asio::io_service io_service;

    Client client(io_service);

    io_service.run();
}