Connect server

The client can use the endpoints returned by DNS query to connect server application. The following is an example:

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

int main()
{
    try
    {
        boost::asio::io_context io_context;

        boost::asio::ip::tcp::resolver resolver{io_context};
        boost::asio::ip::tcp::resolver::results_type endpoints =
                resolver.resolve("google.com", "https");

        boost::asio::ip::tcp::tcp::socket socket{io_context};
        auto endpoint = boost::asio::connect(socket, endpoints);

        std::cout << "Connect to " << endpoint << " successfully!\n";
    }
    catch (std::exception& e)
    {
        std::cerr << e.what() << '\n';
        return -1;
    }

    return 0;
}

The running result is like following:

Connect to 172.217.194.101:443 successfully!

Please notice boost::asio::connect requires the iterator of endpoints. If you just want one specified endpoint, you can use connect member function of socket. Check following code:

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

int main()
{
    try
    {
        boost::asio::io_context io_context;

        boost::asio::ip::tcp::resolver resolver{io_context};
        boost::asio::ip::tcp::resolver::results_type endpoints =
                resolver.resolve("google.com", "https");

        boost::asio::ip::tcp::tcp::socket socket{io_context};
        auto eit = endpoints.cbegin();
        for (; eit != endpoints.cend(); eit++)
        {
            boost::system::error_code ec;
            boost::asio::ip::tcp::endpoint endpoint = *eit;
            socket.connect(endpoint, ec);
            if (!ec)
            {
                std::cout << "Connect to " << endpoint << " successfully!\n";
                break;
            }
        }

        if (eit == endpoints.cend())
        {
            std::cout << "Connect failed!\n";
            return  -1;
        }
    }
    catch (std::exception& e)
    {
        std::cerr << e.what() << '\n';
        return -1;
    }

    return 0;
}

The running result is like this:

Connect to 172.217.194.139:443 successfully!