用asio的定时器实现带超时的connect，备忘

// test.cpp : 定义控制台应用程序的入口点。  
//  
  
#include "stdafx.h"  
#include <boost/asio.hpp>  
#include <boost/bind.hpp>  
#include <boost/date_time/posix_time/posix_time_types.hpp>  
#include <iostream>  
  
using namespace boost::asio;  
using boost::asio::ip::tcp;  
  
class connect_handler  
{  
public:  
    connect_handler(io_service& ios)  
        : io_service_(ios),  
        timer_(ios),  
        socket_(ios)  
    {  
        socket_.async_connect(  
            tcp::endpoint(boost::asio::ip::address_v4::loopback(), 3212),  
            boost::bind(&connect_handler::handle_connect, this,  
            boost::asio::placeholders::error));  
  
        timer_.expires_from_now(boost::posix_time::seconds(5));  
        timer_.async_wait(boost::bind(&connect_handler::close, this));  
    }  
  
    void handle_connect(const boost::system::error_code& err)  
    {  
        if (err)  
        {  
            std::cout << "Connect error: " << err.message() << "\n";  
        }  
        else  
        {  
            std::cout << "Successful connection\n";  
        }  
    }  
  
    void close()  
    {  
        socket_.close();  
    }  
  
private:  
    io_service& io_service_;  
    deadline_timer timer_;  
    tcp::socket socket_;  
};  
  
int main()  
{  
    try  
    {  
        io_service ios;  
        tcp::acceptor a(ios, tcp::endpoint(tcp::v4(), 32123), 1);  
  
        // Make lots of connections so that at least some of them will block.  
        connect_handler ch1(ios);  
        //connect_handler ch2(ios);  
        //connect_handler ch3(ios);  
        //connect_handler ch4(ios);  
        //connect_handler ch5(ios);  
        //connect_handler ch6(ios);  
        //connect_handler ch7(ios);  
        //connect_handler ch8(ios);  
        //connect_handler ch9(ios);  
  
        ios.run();  
    }  
    catch (std::exception& e)  
    {  
        std::cerr << "Exception: " << e.what() << "\n";  
    }  
  
    return 0;  
}  

https://www.cnblogs.com/lidabo/p/3785800.html