如何将异步定时器添加到升级UDP服务器？

Question

我在线获得了这个代码，并且一直试图向它添加一个计时器，以便它每隔一段时间就读一个数据包。我似乎无法弄清楚如何通过一个回调函数来了boost :: async_wait命令，因为我得到这个错误：

server1.cpp: In member function ‘void UDPClient::handle_receive(const boost::system::error_code&, size_t)’: 
server1.cpp:51:66: error: invalid use of non-static member function ‘void UDPClient::time_to_receive(const boost::system::error_code&)’ 
            boost::asio::placeholders::error)); 
                   ^
server1.cpp:33:6: note: declared here 
void UDPClient::time_to_receive(const boost::system::error_code& error) 
     ^~~~~~~~~ 

UDPClient类：

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

using boost::asio::ip::udp; 

class UDPClient 
{ 
public: 
    boost::asio::io_service io_service; 
    udp::socket socket; 
    udp::endpoint receiver_endpoint; 
    boost::asio::deadline_timer timer; 
    boost::array<char, 1024> recv_buffer; 

    UDPClient(); 
    void time_to_receive(const boost::system::error_code& error); 
    void do_receive(); 
    void handle_receive(const boost::system::error_code& error, size_t); 
}; 

UDPClient::UDPClient() 
    : io_service(), 
     socket(io_service, {udp::v4(), 3643}), 
     timer(io_service, boost::posix_time::seconds(2)) 
{ 
    do_receive(); 
    io_service.run(); 
} 

void UDPClient::time_to_receive(const boost::system::error_code& error) 
{ 
    do_receive(); 
} 

void UDPClient::do_receive() 
{ 
    socket.async_receive_from(boost::asio::buffer(recv_buffer), receiver_endpoint, 
           boost::bind(&UDPClient::handle_receive, this, 
           boost::asio::placeholders::error, 
           boost::asio::placeholders::bytes_transferred)); 
} 

void UDPClient::handle_receive(const boost::system::error_code& error, size_t bytes_transferred) 
{ 
    std::cout << "Received: '" << std::string(recv_buffer.begin(), recv_buffer.begin()+bytes_transferred) << "'\n"; 

    timer.async_wait(boost::bind(time_to_receive, 
           boost::asio::placeholders::error)); 
} 

int main() 
{ 
    UDPClient updclient; 
} 

一个问题，我试图用这个代码回答是，如果我用一堆UDP数据包从客户端发送服务器垃圾邮件，服务器会在async_wait期间忽略所有数据包吗？

此外，我的主要目标是将此代码放入我拥有的quadcopter代码中。它是否会按照写入的方式实例化这个类并让它从地面站读取数据包以获取用户输入？

Answer 1

使用bind和成员函数的方式是错误的。使用它如下所示：

timer.async_wait(boost::bind(&UDPClient::time_to_receive, this, 
          boost::asio::placeholders::error)); 

至于为什么它是这样的，我会建议你阅读增强文档。

另外，我修改了代码，使其实际上像服务器一样运行而不退出。为此，我做了以下2个更改：

1. 初始化io_service在main函数中并将其引用给类。
2. 初始化io_service_work对象。这作为io_service的常年工作来源。因此，io_service永远不会从run函数返回，除非work对象被销毁。

完整的源：

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

using boost::asio::ip::udp; 

class UDPClient 
{ 
public: 
    boost::asio::io_service& io_service; 
    udp::socket socket; 
    udp::endpoint receiver_endpoint; 
    boost::asio::deadline_timer timer; 
    boost::array<char, 1024> recv_buffer; 

    UDPClient(boost::asio::io_service&); 
    void time_to_receive(const boost::system::error_code& error); 
    void do_receive(); 
    void handle_receive(const boost::system::error_code& error, size_t); 
}; 

UDPClient::UDPClient(boost::asio::io_service& ios) 
    : io_service(ios), 
     socket(io_service, {udp::v4(), 3643}), 
     timer(io_service, boost::posix_time::seconds(2)) 
{ 
    do_receive(); 
} 

void UDPClient::time_to_receive(const boost::system::error_code& error) 
{ 
    do_receive(); 
} 

void UDPClient::do_receive() 
{ 
    socket.async_receive_from(boost::asio::buffer(recv_buffer), receiver_endpoint, 
           boost::bind(&UDPClient::handle_receive, this, 
           boost::asio::placeholders::error, 
           boost::asio::placeholders::bytes_transferred)); 
} 

void UDPClient::handle_receive(const boost::system::error_code& error, size_t bytes_transferred) 
{ 
    std::cout << "Received: '" << std::string(recv_buffer.begin(), recv_buffer.begin()+bytes_transferred) << "'\n"; 
    timer.expires_from_now(boost::posix_time::seconds(2)); 
    timer.async_wait(boost::bind(&UDPClient::time_to_receive, this, 
           boost::asio::placeholders::error)); 
} 

int main() 
{ 
    boost::asio::io_service ios; 
    boost::asio::io_service::work wrk(ios); 
    UDPClient updclient(ios); 
    ios.run(); 
} 

注：即使它是一个服务器，这个类是名客户。我忽略了:)