当断开连接时，boost :: asio :: async_write的WriteHandler无法正常工作(防火墙/手动断开网络连接) [英] WriteHandler from boost::asio::async_write doesn't work properly when connection is dropped (firewall / manual disconecting the network)

问题描述

我一直在尝试使用boost :: asio编写客户端-服务器应用程序，总体上该应用程序运行良好，但是当连接(客户端<>服务器之间)之间的连接被防火墙或手动禁用newtwork卡丢弃.

I've been trying to write a client-server application using boost::asio, overall the application works great but I've stumbled over a problem regarding the data provided by 'WriteHandler' ( async_write function) when the connoction (between client <> server) is droped by a firewalll or by manualy disabling a newtwork card.

这是代码段:

void write(const CommunicatorMessage & msg, std::function<void(bool)> writeCallback)
        {
            io_service.dispatch(
                [this, msg, writeCallback]()
            {
                boost::asio::async_write(socket, boost::asio::buffer(msg.data(), msg.length()), [this, msg, writeCallback](boost::system::error_code ec, std::size_t length)
                {
                    writeCallback(ec != 0);
                    if (!ec)
                    {
                        LOG_DEBUG("Number of bytes written into the buffer: " << length << " Error code: " << ec);
                        LOG_DEBUG("Successfully send msg: " << msg);
                    }
                    else
                    {
                        LOG_ERROR("Failed sending msg: " << msg);
                        throw std::exception(ec.message().c_str());
                    }
                });
            });
        }

即使数据没有到达服务器，来自Writehandler的数据也是有效的(错误代码为0，bytes_transferred是正确的).我已经用Wireshark跟踪了整个流程(这是一个屏幕截图的链接链接)

The data from the Writehandler is valid (the error code is 0, bytes_transferred are correct), even if the data doesn't arrive on the server. I've tracked with Wireshark the whole flow( here's a link with the a screenshot Link)

推荐答案

当 async_write 向您发送成功时，表示已成功写入内核缓冲区.但是，它的不能保证的数据包已传递.

When async_write send you success it means it sucessfully written to kernel's buffer. But, its not guaranteed packet was delivered.

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