boost::asio::async_read 无限循环，接收数据为零字节

Posted 2023-02-16

【中文标题】boost::asio::async_read 无限循环，接收数据为零字节

【英文标题】：boost::asio::async_read loops infinite with zero byte of received data

【发布时间】：2017-07-27 18:55:06

【问题描述】：

我正在尝试编写基于 IO_Service 的异步 TCP 客户端，其中 Async_write 工作正常，但 async_read 在无限循环中运行。在我尝试纠正这个问题的过程中，我发现在所有其他情况下 async_read 只是停止接收数据，在我停止服务器之前它什么也没有收到。以下是我在发布查询之前尝试过的代码和链接。

我尝试过的建议是exactly as mine、2、3and，但在所有情况下，我的 async_read 处理程序都没有读取任何内容。在一种也是唯一一种情况下，当我将缓冲区设置为 boost::asio::mutable_buffer bytes; 时，它会启动无限循环，而在其他情况下，我尝试了 boost::array<char, 512> bytes;、boost::asio::streambuf bytes; 和 char bytes[512];，其中未引发 async_read 处理程序。

在经历了所有这些解决方案之后，我现在很困惑：会不会是缓冲区的问题？在传递给阅读之前我需要初始化它吗 ?

请指导。

ScalableSocket::ScalableSocket()

    //ctor

    using namespace boost::asio;
    service = boost::make_shared<io_service>();
    work =    boost::make_shared<io_service::work>(*service );
    strand  = boost::make_shared<io_service::strand>( *service );
    worker_threads = boost::make_shared<boost::thread_group>();



        worker_threads->create_thread(boost::bind(&ScalableSocket::WorkerThread,this));


    resolver = boost::make_shared<boost::asio::ip::tcp::resolver> (*service);

    tcp_socket= boost::make_shared<boost::asio::ip::tcp::socket> (*service);

    boost::asio::ip::tcp::resolver::query q(boost::asio::ip::tcp::v4(),"192.168.100.96","9602");

    boost::asio::ip::tcp::resolver::iterator it = resolver->resolve(q);

    boost::asio::async_connect(*tcp_socket,it,boost::bind(&ScalableSocket::connect_handler,this,boost::asio::placeholders::error));

    tcp_socket->set_option(boost::asio::ip::tcp::no_delay(true) );



ScalableSocket::~ScalableSocket()

    //dtor



void ScalableSocket::PublishPost()

    strand->post(boost::bind(&ScalableSocket::OnSend,this));



void ScalableSocket::OnSend()



    boost::array<char, 6> a =  'a', 'b', 'c', 'd', 'e' ;

    boost::asio::async_write(*tcp_socket,boost::asio::buffer(a),
                                    boost::bind(&ScalableSocket::write_handler, this, boost::asio::placeholders::error,boost::asio::placeholders::bytes_transferred));





void ScalableSocket::WorkerThread()

    while( true )
    
        try
        
            boost::system::error_code ec;
            service->run( ec );
            if( ec )
            
                ///LOGE(ec);
            
            break;
        
        catch( std::exception & ex )
        
            ///LOGE(ex.what());
        
    


void ScalableSocket::connect_handler(const boost::system::error_code &ec)

    if (!ec)
    

    PublishPost();




/* boost::asio::async_read(*tcp_socket,
                                boost::asio::buffer(bytes),
                                boost::bind(&ScalableSocket::read_handler, this,
                                            boost::asio::placeholders::error,boost::asio::placeholders::bytes_transferred));
*/

        ///https://***.com/questions/4527443/problems-using-boostasioasync-read

        boost::shared_ptr<boost::array<char, 512>> buf(new boost::array<char, 512>);


        boost::asio::async_read(*tcp_socket,boost::asio::buffer(*buf),
                                boost::bind(&ScalableSocket::read_handler, this,buf,
                                boost::asio::placeholders::error,boost::asio::placeholders::bytes_transferred));

    
    else
    
        cout<<" Some error connecting to Exchange  "<< ec.message()<<endl;

    




void ScalableSocket::OnTimer(const boost::system::error_code &ec)

    if(!ec)
    
        printf("\n\n Heartbeat event raised sending KeepAlive to exchange \n\n");
        PublishPost();
        HeartBeatTimer->async_wait(boost::bind(&ScalableSocket::OnTimer,this, boost::asio::placeholders::error));
    


void ScalableSocket::recvData()

    boost::system::error_code error;
    boost::array<char, 1024> buf;

    //for(;;)
    
        size_t len = tcp_socket->read_some(boost::asio::buffer(buf), error);

        cout<<"\n Recv data size is "<<len;

    


void ScalableSocket::read_handler(boost::shared_ptr<boost::array<char, 512>> buf,const boost::system::error_code &ec,std::size_t bytes_transferred)



    if (!ec )//&& bytes_transferred > 0)
    

        ///recvData(); /// If i enable this code during infinite loop it start getting data that means socket has no issue

        cout << " Data size recieved "<< bytes_transferred<<endl;




            boost::asio::async_read(*tcp_socket,boost::asio::buffer(*buf),
                                boost::bind(&ScalableSocket::read_handler, this,buf,
                                boost::asio::placeholders::error,boost::asio::placeholders::bytes_transferred));
    
    else
    
        /// Some issue with socket publish error , inform user and reconnect
        cout<<" Some error reading data from Exchange  "<< ec.message()<<endl;

    


void ScalableSocket::write_handler(const boost::system::error_code& error,std::size_t bytes_transferred)

    if(!error)
    
        /// data Sent successfully
        cout<< " Data sent size "<< bytes_transferred<<endl;

    
    else
    
        cout<<" Some error sending data to Exchange  "<< error.message()<<endl;
    

【问题讨论】：

但是你知道asnyc_read 不会“返回”/调用处理程序，直到给定的缓冲区完全填满，对吧？

我使用了这种 512 类型的缓冲区，一旦我使用 boost 流缓冲区或可变缓冲区未能接收到任何东西，然后我尝试在堆栈本身的一些解决方案之后使用该 512 的东西

一些标点符号有助于识别您的评论。尝试发送 512 字节及以上的数据，看看是否正确接收。

感谢@Blacktempel 救了我。你是 100% 正确的。都是我的错。将 asio::async_read 替换为 socket.async_read_some 并且它起作用了。

【参考方案1】：

asnyc_read不会“返回”/调用处理程序，直到给定的缓冲区完全填满。

asnyc_read_some 将在读取一些字节后返回。这可能是您正在寻找的功能。

记得使用asnyc_read_some 正确处理接收到的数据。如果您发送 512 个字节，它可能会在几次读取中到达，具体取决于机器。