Question

使用asio 1.66.0 Windows实现

时遇到以下情况我遇到了麻烦

bind socket
运行io_context
停止io_context
关闭套接字
重启io_context
重复1-4

在第二次迭代中调用io_context :: run后跟系统错误995

I / O操作因线程退出或中断而中止申请要求

看起来这个错误来自套接字闭包：asio使用PostQueuedCompletionStatus / GetQueuedCompletionStatus来表示自己调用了io_context :: stop。但是由socket_.async_receive_from中的WSARecvFrom排队的I / O操作失败，因为socket已关闭，并且在下一次调用io_context :: run时，它是我在处理程序中传递给socket_.async_receive_from的第一个。

asio io_context的意图是什么？如何在连续迭代中避免此错误？

如果我通过关闭套接字来停止io_context :: run，那么所有工作都会有相同的错误并且看起来很脏。另一个奇怪的事情是，如果我在收到错误后继续使用do_receive，我将收到与先前迭代次数一样多的错误，然后我将从套接字接收数据。

// based on boost_asio/example/cpp11/multicast/receiver.cpp
// https://www.boost.org/doc/libs/1_66_0/doc/html/boost_asio/example/cpp11/multicast/receiver.cpp

#include <array>
#include <iostream>
#include <string>
#include <boost/asio.hpp>
#include <future>
#include <chrono>
#include <thread>

using namespace std::chrono_literals;

constexpr short multicast_port = 30001;

class receiver
{
public:
    explicit receiver(boost::asio::io_context& io_context) : socket_(io_context)
    {}

    ~receiver()
    {
        close();
    }

    void open(
        const boost::asio::ip::address& listen_address,
        const boost::asio::ip::address& multicast_address)
    {
        // Create the socket so that multiple may be bound to the same address.
        boost::asio::ip::udp::endpoint listen_endpoint(
            listen_address, multicast_port);
        socket_.open(listen_endpoint.protocol());
        socket_.set_option(boost::asio::ip::udp::socket::reuse_address(true));
        socket_.bind(listen_endpoint);

        // Join the multicast group.
        socket_.set_option(
            boost::asio::ip::multicast::join_group(multicast_address));

        do_receive();
    }

    void close()
    {
        if (socket_.is_open())
        {
            socket_.close();
        }
    }

private:
    void do_receive()
    {
        socket_.async_receive_from(
            boost::asio::buffer(data_), sender_endpoint_,
            [this](boost::system::error_code ec, std::size_t length)
            {
                if (!ec)
                {
                    std::cout.write(data_.data(), length);
                    std::cout << std::endl;

                    do_receive();
                }
                else
                {
                    // A call to io_context::run in second iteration is followed by system error 995
                    std::cout << ec.message() << std::endl;
                }
            });
    }

    boost::asio::ip::udp::socket socket_;
    boost::asio::ip::udp::endpoint sender_endpoint_;
    std::array<char, 1024> data_;
};

int main(int argc, char* argv[])
{
    try
    {
        const std::string listen_address = "0.0.0.0";
        const std::string multicast_address = "239.255.0.1";

        boost::asio::io_context io_context;
        receiver r(io_context);
        std::future<void> fut;

        for (int i = 5; i > 0; --i)
        {
            io_context.restart();
            r.open(
                boost::asio::ip::make_address(listen_address),
                boost::asio::ip::make_address(multicast_address));
            fut = std::async(std::launch::async, [&](){ io_context.run(); });
            std::this_thread::sleep_for(3s);
            io_context.stop();
            fut.get();
            r.close();
        }

    }
    catch (std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}

C ++ Boost :: ASIO：第二次调用io_context :: run后出现系统错误995

0 个答案: