“现有连接被远程主机强行关闭".在侦听传入数据时

在使用Boost asio时，我偶然发现了一些我不太了解的奇怪行为.我编写了一个最小的测试程序来复制该问题:

When working with boost asio, I've stumbled upon some weird behavior, which I don't quite understand. I wrote a minimal test-program to replicate the problem:

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

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

int main(int argc,char *argv[])
{
    boost::asio::io_service ioService;
    udp::resolver resolver(ioService);

    udp::resolver::query queryListen("127.0.0.1","50001");
    auto epListen = *resolver.resolve(queryListen);
    udp::socket socket(ioService,epListen);

    udp::resolver::query querySend("127.0.0.1","55006");
    auto epSend = *resolver.resolve(querySend);
    boost::system::error_code err;
    std::array<char,12> buffer = {'1','2','3','4','5','6','7','8','9','10','11','12'};
    socket.send_to(
        boost::asio::buffer(&buffer[0],buffer.size()),
        epSend,0,err
    );
    if(!err)
    {
        std::cout<<"Sent successfully!"<<std::endl;
        auto numBytes = socket.receive(
            boost::asio::buffer(&buffer[0],buffer.size()),0,
            err
        );
        if(!err)
            std::cout<<"Received "<<numBytes<<" bytes successfully!"<<std::endl;
        else
            std::cout<<"Unable to receive: "<<err.message()<<std::endl; // This is where I'm getting the message "An existing connection was forcibly closed by the remote host"
    }
    else
        std::cout<<"Unable to send: "<<err.message()<<std::endl;
    for(;;);
    return 0;
}

如果"send_to"呼叫的目标端点存在并且正在侦听，则此程序运行良好.数据已正确发送，然后等待传入数据.

If the destination endpoint for the 'send_to'-call exists and is listening, this program runs just fine. The data is sent correctly, and it then waits for incoming data.

但是，如果目标端点不存在，则该行为非常意外. 'send_to'调用仍会分派数据，而没有任何错误，但是当尝试接收数据时，'receive'调用会立即返回，并且我收到现有连接被远程主机强行关闭"错误.这对我来说没有任何意义.首先，没有远程主机，因为没有数据发送到侦听器端口.其次，据我了解，该程序的接收部分和发送部分应该是完全独立的，并且互不影响.我在这个假设上错了吗?

However, if the destination endpoint doesn't exist, the behavior is rather unexpected. The 'send_to'-call still dispatches the data without any errors, but when trying to receive data, the 'receive'-call immediately returns, and I'm getting a "An existing connection was forcibly closed by the remote host" error. This doesn't make any sense to me. First of all, there is no remote host, since there is no data being sent to the listener port. Secondly, from what I understand, the receiving- and the sending-part in this program should be completely independent, and shouldn't affect each other at all. Am I wrong in that assumption?

//

我刚刚意识到，该消息没有任何意义还有另一个原因.我使用的是无连接的UDP procotol，那么什么连接"已关闭?

I've just realized that there's another reason why that message doesn't make any sense. I'm using the UDP procotol, which is connectionless, so what 'connection' was closed?