那些遇到过的问题

提升异步tcp客户端

Tor*_*ius 5 c++ client boost boost-asio

我刚刚开始使用boost.我正在使用异步套接字编写TCP客户端服务器.

任务如下:

  1. 客户端向服务器发送一个号码
  2. 客户端可以在收到服务器的答案之前发送另一个nubmer.
  3. 服务器接收一个号码,用它做一些计算并将结果发送回客户端.
  4. 多个客户端可以连接到服务器.

现在工作如下

  • 从客户端向服务器发送号码
  • 服务器接收当前线程中的数字并在OnReceive处理程序中计算(我知道这很糟糕......但我应该如何开始一个新的线程来并行执行计算)
  • 服务器发回应答但客户端已断开连接

如何允许客户端从键盘输入数字并同时等待服务器的回答？

为什么我的客户不等待服务器的答案？

客户端代码:

using boost::asio::ip::tcp;

class TCPClient
{
    public:
        TCPClient(boost::asio::io_service& IO_Service, tcp::resolver::iterator EndPointIter);
        void Close();

    private:
        boost::asio::io_service& m_IOService;
        tcp::socket m_Socket;

        string m_SendBuffer;
        static const size_t m_BufLen = 100;
        char m_RecieveBuffer[m_BufLen*2];

        void OnConnect(const boost::system::error_code& ErrorCode, tcp::resolver::iterator EndPointIter);
        void OnReceive(const boost::system::error_code& ErrorCode);
        void OnSend(const boost::system::error_code& ErrorCode);
        void DoClose();
};

TCPClient::TCPClient(boost::asio::io_service& IO_Service, tcp::resolver::iterator EndPointIter)
: m_IOService(IO_Service), m_Socket(IO_Service), m_SendBuffer("")
{
    tcp::endpoint EndPoint = *EndPointIter;

    m_Socket.async_connect(EndPoint,
        boost::bind(&TCPClient::OnConnect, this, boost::asio::placeholders::error, ++EndPointIter));
}

void TCPClient::Close()
{
    m_IOService.post(
        boost::bind(&TCPClient::DoClose, this));
}
void TCPClient::OnConnect(const boost::system::error_code& ErrorCode, tcp::resolver::iterator EndPointIter)
{
    cout << "OnConnect..." << endl;
    if (ErrorCode == 0)
    {
        cin >> m_SendBuffer;
        cout << "Entered: " << m_SendBuffer << endl;
        m_SendBuffer += "\0";

        m_Socket.async_send(boost::asio::buffer(m_SendBuffer.c_str(),m_SendBuffer.length()+1),
            boost::bind(&TCPClient::OnSend, this,
            boost::asio::placeholders::error));
    } 
    else if (EndPointIter != tcp::resolver::iterator())
    {
        m_Socket.close();
        tcp::endpoint EndPoint = *EndPointIter;

        m_Socket.async_connect(EndPoint, 
            boost::bind(&TCPClient::OnConnect, this, boost::asio::placeholders::error, ++EndPointIter));
    }
}

void TCPClient::OnReceive(const boost::system::error_code& ErrorCode)
{
    cout << "receiving..." << endl;
    if (ErrorCode == 0)
    {
        cout << m_RecieveBuffer << endl;

        m_Socket.async_receive(boost::asio::buffer(m_RecieveBuffer, m_BufLen),
            boost::bind(&TCPClient::OnReceive, this, boost::asio::placeholders::error));
    } 
    else 
    {
        cout << "ERROR! OnReceive..." << endl;
        DoClose();
    }
}

void TCPClient::OnSend(const boost::system::error_code& ErrorCode)
{
    cout << "sending..." << endl;
    if (!ErrorCode)
    {
        cout << "\""<< m_SendBuffer <<"\" has been sent" << endl;
        m_SendBuffer = "";

        m_Socket.async_receive(boost::asio::buffer(m_RecieveBuffer, m_BufLen),
            boost::bind(&TCPClient::OnReceive, this, boost::asio::placeholders::error));
    }
    else
    {
        cout << "OnSend closing" << endl;
        DoClose();
    }

}

void TCPClient::DoClose()
{
    m_Socket.close();
}

int main()
{
    try 
    {
        cout << "Client is starting..." << endl;
        boost::asio::io_service IO_Service;

        tcp::resolver Resolver(IO_Service);

        string port = "13";
        tcp::resolver::query Query("127.0.0.1", port);

        tcp::resolver::iterator EndPointIterator = Resolver.resolve(Query);

        TCPClient Client(IO_Service, EndPointIterator);

        cout << "Client is started!" << endl;

        cout << "Enter a query string " << endl;

        boost::thread ClientThread(boost::bind(&boost::asio::io_service::run, &IO_Service));

        Client.Close();
        ClientThread.join();
    } 
    catch (exception& e)
    {
        cerr << e.what() << endl;
    }

    cout << "\nClosing";
    getch();
}
Run Code Online (Sandbox Code Playgroud)

这是控制台的输出

Client is starting...
Client is started!
OnConnect...
12
Entered: 12
sending...
"12" has been sent
receiving...
ERROR! OnReceive...

Closing
Run Code Online (Sandbox Code Playgroud)

服务器部分

class Session
{
    public:
        Session(boost::asio::io_service& io_service)
            : socket_(io_service)
        {
            dataRx[0] = '\0';
            dataTx[0] = '\0';
        }

        tcp::socket& socket()
        {
            return socket_;
        }

        void start()
        {
            socket_.async_read_some(boost::asio::buffer(dataRx, max_length),
                boost::bind(&Session::handle_read, this,
                boost::asio::placeholders::error,
                boost::asio::placeholders::bytes_transferred));
        }

        void handle_read(const boost::system::error_code& error, size_t bytes_transferred)
        {
            cout << "reading..." << endl;
            cout << "Data: " << dataRx << endl;

            if (!error)
            {
                if (!isValidData())
                {
                    cout << "Bad data!" << endl;
                    sprintf(dataTx, "Bad data!\0");
                    dataRx[0] = '\0';
                }
                else
                {
                    sprintf(dataTx, getFactorization().c_str());
                    dataRx[0] = '\0';
                }

                boost::asio::async_write(socket_,
                    boost::asio::buffer(dataTx, max_length*2),
                    boost::bind(&Session::handle_write, this,
                    boost::asio::placeholders::error));
            }
            else
            {
                delete this;
            }
        }

        void handle_write(const boost::system::error_code& error)
        {
            cout << "writing..." << endl;
            if (!error)
            {
                cout << "dataTx sent: " << dataTx << endl;
                dataTx[0] = '\0';

                socket_.async_read_some(boost::asio::buffer(dataRx, max_length),
                    boost::bind(&Session::handle_read, this,
                    boost::asio::placeholders::error,
                    boost::asio::placeholders::bytes_transferred));
            }
            else
            {
                delete this;
            }
        }

        string getFactorization() const
        {
            //Do something
        }

        bool isValidData()
        {
            locale loc; 
            for (int i = 0; i < strlen(dataRx); i++)
                if (!isdigit(dataRx[i],loc))
                    return false;

            return true;
        }

    private:
        tcp::socket socket_;
        static const size_t max_length = 100;
        char dataRx[max_length];
        char dataTx[max_length*2];
};

class Server
{
    public:
        Server(boost::asio::io_service& io_service, short port)
            : io_service_(io_service),
            acceptor_(io_service, tcp::endpoint(tcp::v4(), port))
        {
            Session* new_session = new Session(io_service_);
            acceptor_.async_accept(new_session->socket(),
                boost::bind(&Server::handle_accept, this, new_session,
                boost::asio::placeholders::error));
        }

        void handle_accept(Session* new_session, const boost::system::error_code& error)
        {
            if (!error)
            {
                new_session->start();
                new_session = new Session(io_service_);
                acceptor_.async_accept(new_session->socket(),
                    boost::bind(&Server::handle_accept, this, new_session,
                    boost::asio::placeholders::error));
            }
            else
            {
                delete new_session;
            }
        }

    private:
        boost::asio::io_service& io_service_;
        tcp::acceptor acceptor_;
};

int main(int argc, char* argv[])
{
    cout << "Server is runing..." << endl;
    try
    {
        boost::asio::io_service io_service;

        int port = 13;
        Server s(io_service, port);
        cout << "Server is run!" << endl;
        io_service.run();
    }
    catch (boost::system::error_code& e)
    {
        std::cerr << e << "\n";
    }
    catch (std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }

    return 0;
}
Run Code Online (Sandbox Code Playgroud)

服务器的输出

Server is runing...
Server is run!
reading...
Data: 12
writing...
dataTx sent: 13    //just send back received ++number
reading...
Data:
Run Code Online (Sandbox Code Playgroud)

非常感谢您的帮助

========

添加

好的,我明白了.但检查ErrorCode == boost :: asio :: error :: eof不起作用......我做错了什么？

else if (ErrorCode == boost::asio::error::eof)
{
    cout << "boost::asio::error::eof in OnReceive!" << endl;
}
else 
{
    cout << "ERROR! OnReceive..." << ErrorCode << endl;
    DoClose();
}
Run Code Online (Sandbox Code Playgroud)

打印出来ERROR! OnReceive...system:10009似乎是我的比较是不正确的

========

添加

我找到了根本原因.我已声明使用async_receive(而不是async_read_some)并将线条main转换为

ClientThread.join();
Client.Close();
Run Code Online (Sandbox Code Playgroud)

现在它工作正常!

现在我正在尝试同时从/向套接字读取和写入数据(因为客户端应该能够在收到服务器的回复之前发送其他请求.

在OnConnect函数中我创建了boost线程:

boost::thread addMsgThread(boost::bind(&TCPClient::addMsgLoop, this));
boost::thread receivingThread(boost::bind(&TCPClient::startReceiving, this));
boost::thread sendingThread(boost::bind(&TCPClient::startSending, this));
Run Code Online (Sandbox Code Playgroud)

与实施

void TCPClient::startReceiving()
{
    cout << "receiving..." << endl;
    m_RecieveBuffer[0] = '\0';
    m_Socket.async_receive(boost::asio::buffer(m_RecieveBuffer, m_BufLen),
        boost::bind(&TCPClient::receivingLoop, this, boost::asio::placeholders::error)); //runtime error here
    cout << "m_RecieveBuffer = " << m_RecieveBuffer << endl;
}

void TCPClient::receivingLoop(const boost::system::error_code& ErrorCode)
{
    cout << "receiving..." << endl;
    if (ErrorCode == 0)
    {
        cout << "m_RecieveBuffer = " << m_RecieveBuffer << endl;

        m_Socket.async_receive(boost::asio::buffer(m_RecieveBuffer, m_BufLen),
            boost::bind(&TCPClient::receivingLoop, this, boost::asio::placeholders::error));
    }
    else 
    {
        cout << "ERROR! receivingLoop..." << ErrorCode << endl;
        DoClose();
    }
}

void TCPClient::addMsgLoop()
{
    while (true)
    {
        string tmp;
        cin >> tmp;

        cout << "Entered: " << tmp << endl;
        tmp += "\0";

        try
        {
            msgQueue.push(tmp);
        }
        catch(exception &e)
        {
            cerr << "Canno add msg to send queue... " << e.what() << endl;
        }
    }
}
Run Code Online (Sandbox Code Playgroud)

两个receive和send线程的问题都是一样的:运行时错误(在boost库中的某处写入访问冲突).

void TCPClient::startReceiving()
{
     ...
     m_Socket.async_receive(); //runtime error here
}
Run Code Online (Sandbox Code Playgroud)

在后续版本中一切正常(但我不知道如何在回答之前实现多个发送).任何人都可以告诉我如何解决问题或如何通过另一种方式实现这个问题？可能是汇集可以帮助,但我现在肯定这是好方法.

Vik*_*kas 4

boost::asio::ip::tcp::socket::async_read_some顾名思义，不保证读取完整数据。它将error对象设置为boost::asio::error::eof客户端完成写入时。

您收到的错误是因为：

服务器部分

        if (!error)
        {
            ...
        }
        else
        {
            delete this;
        }
Run Code Online (Sandbox Code Playgroud)

在else块中，您假设这是一个错误情况并关闭连接。这并非总是如此。在此之前else您需要检查error == boost::asio::error::eof.

除了读取处理程序中的这一点之外，您应该继续收集缓冲区中读取的所有内容，直到您点击error == boost::asio::error::eof。只有这样，您才应该验证读取的数据并将其写回客户端。

查看示例部分中的 HTTP 服务器1、2、3实现。

更新：回答更新的问题

更新后的代码存在线程同步问题。

  1. msgQueue从两个或多个线程同时访问，无需任何锁定。
  2. 同一个套接字上的读和写可以同时调用。

如果我正确理解你的问题，你想要：

  1. 获取用户输入并将其发送到服务器。
  2. 同时不断接收服务器的响应。

您可以使用两个boost::asio::io_service::strand来执行这两个任务。使用 Asio 时，链是同步任务的方式。Asio 确保链中发布的任务同步执行。

  1. 在strand1发布send任务时，如下所示：read_user_input -> send_to_server -> handle_send -> read_user_input

  2. 在strand2发布read任务时，如下所示：read_some -> handle_read -> read_some

这将确保msgQueue不会同时从两个线程访问。使用两个套接字对服务器进行读取和写入，以确保不会在同一个套接字上调用同时读取和写入。

归档时间：

查看次数：

13926 次

最近记录：

13 年 前
相关归档
为什么C++ 11删除的函数参与重载解析？ 86
调用构造函数重新初始化对象 61
为什么模板参数替换的顺序很重要？ 56
可选函数参数:使用默认参数(NULL)或重载函数？ 41
在函数中返回大对象 40
C++ stl stringstream直接缓冲区访问 30
SDL2纹理有什么意义？ 27
boost是否具有比STL更简单的set操作的数据类型？ 26
Boost.Pointer容器在C++ 11/14中被std :: unique_ptr淘汰了？ 9
将IP地址从std :: string转换为boost :: uint32 1
难疑归档
在Python中调用外部命令 4553
如何在JavaScript中创建字符串大写的第一个字母？ 3565
如何删除远程标签？ 3121
如何检查字符串是否包含特定单词？ 2663
我为什么要使用指针而不是对象本身？ 1532
从JSON文件中解析值？ 1400
为什么不从List <T>继承？ 1299
检查Bash shell脚本中是否存在输入参数 1223
window.onload vs $(document).ready() 1205
如何以CSV格式输出MySQL查询结果？ 1118