Question

UPDATE_2 我最终使用

if (socket.available())

如果套接字上有数据，我会读取它，如果没有，我跳过。

已更新 我有个问题。 io_service :: run（）永远不会在以下代码片段中返回：

客户方：

#include <iostream>

#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/array.hpp>

using namespace std;
using boost::asio::ip::tcp;

void handler(
    const boost::system::error_code &error,
    size_t bytes_transferred
)
{
    cout << "Handler called" << endl;
}

int main()
{
    //establishing connection
    boost::asio::io_service io_service;
    tcp::socket socket(io_service);
    tcp::resolver resolver(io_service);
    tcp::resolver::query query("localhost", "17073");
    tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
    boost::asio::connect(socket, endpoint_iterator);
    //connection established

    boost::array<char, 128> buf;
    socket.async_read_some(boost::asio::buffer(buf), boost::bind(handler, _1, _2));

    //async_read_some returns

    io_service.run();       //I suppose that handler_for_async_response is called if:
                            //1) EOF was read (no data read twice) by async_read_some
                            //2) something was in fact read
                            //is this right?

    //execution does not get here

    return 0;
}

服务器端（仅接受连接并在那里无所事事地挂起）：

#include <iostream>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/array.hpp>

using namespace std;
using boost::asio::ip::tcp;

int main()
{
    //establishing connection
    boost::asio::io_service io_service;
    tcp::socket             socket(io_service);
    tcp::acceptor           acceptor(io_service, tcp::endpoint(tcp::v4(), 17073));

    acceptor.accept(socket);

    std::cout << "connection has been established!" << std::endl;
    //connection established

    while (true)
    {
        //do nothing
    }

    return 0;
}

我要做的是查看套接字上是否有任何数据。如果是 - 那么请阅读它，如果没有 - 那么继续前进。

PS我打算从套接字读取并写入它。

无论如何，我是提升:: asio的新手，我希望有人可以告诉我我做错了什么。谢谢！

Answer 1

更新使用代码回复更新的问题：

您的客户端正在等待128个字节或EOF。这些都没有，因为服务器没有发送任何东西（但是没有关闭连接）。

要么改变

客户，例如
- 不要等到实际数据到达
```
boost::array<char, 0> buf;
```
- 或者socket.cancel()之后deadline_timer（或者等等。
服务器，例如用真正的套接字写

这是一个样本

<强> Live On Coliru

#include <boost/array.hpp>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <iostream>

using boost::asio::ip::tcp;
using namespace std;

#ifdef SERVER
    int main()
    {
        //establishing connection
        boost::asio::io_service io_service;
        tcp::socket             socket(io_service);
        tcp::acceptor           acceptor(io_service, tcp::endpoint(tcp::v4(), 17073));

        acceptor.accept(socket);

        std::cout << "connection has been established!" << std::endl;
        //connection established

        socket.send(boost::asio::buffer(std::string("Hello world\n")));
    }
#else
    void handler(
        boost::array<char, 128> const& buf,
        const boost::system::error_code &error,
        size_t bytes_transferred
    )
    {
        cout << "Handler called (" << error.message() << "): "  << endl;
        cout.write(buf.data(), bytes_transferred);
    }

    int main()
    {
        //establishing connection
        boost::asio::io_service io_service;
        tcp::socket socket(io_service);
        tcp::resolver resolver(io_service);
        tcp::resolver::query query("127.0.0.1", "17073");
        tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
        boost::asio::connect(socket, endpoint_iterator);
        //connection established

        boost::array<char, 128> buf;
        socket.async_read_some(boost::asio::buffer(buf), boost::bind(handler, boost::ref(buf), _1, _2));

        //async_read_some returns

        io_service.run();       //I suppose that handler_for_async_response is called if:
                                //1) EOF was read (no data read twice) by async_read_some
                                //2) something was in fact read
                                //is this right?

        //execution does not get here

        return 0;
    }
#endif

打印：

//(server)
connection has been established!
//(client)
Handler called (Success):

Hello world

您必须决定同步或异步编程。

在这种情况下，我认为您可能真的在寻找tcp::istream。

当任务用完时运行返回：

http://www.boost.org/doc/libs/1_59_0/doc/html/boost_asio/reference/io_service/run/overload1.html

run()函数阻塞，直到所有工作完成，并且没有更多处理程序要调度，或者直到io_service已停止。

多个线程可以调用run()函数来设置一个线程池，io_service可以从中执行处理程序。在池中等待的所有线程都是等效的，io_service可以选择其中任何一个来调用处理程序。

run()函数的正常退出意味着io_service对象停止（stopped（）函数返回true）。除非事先致电run()，否则对[{1}}，run_one()，poll()或poll_one()的后续调用将立即返回。

所以你还有其他工作待定（io_service :: work？）。检查一下。使您的代码成为SSCCE，我们将能够看到更多。

io_service :: run（）永远不会返回

1 个答案:

Hello world