boost :: asio无法连接到没有WLAN的localhost

Question

在我的计算机(Surface Pro 2)上,只有一个网络适配器,它是一个无线LAN适配器.

我参与了一个小型的C++项目,它使用boost :: asio连接到localhost并完成它的工作,一切都很好.

但今天我发现,如果我从互联网断开WLAN,这个程序不起作用.

boost :: asio的解析器会抛出异常:

tcp::resolver::query query("localhost", "10127");
tcp::resolver resolver(io_service_);
tcp::resolver::iterator iterator;

try {
    iterator = resolver.resolve(query);
}
catch (boost::system::system_error& e) {
    log(e.what());
}

并且错误消息是:请求的名称有效,但未找到所请求类型的数据.

ping到localhost就可以了.

我感到困惑,本地网络程序是否需要互联网？本地网络程序是否需要LAN适配器？为什么ping工作正常？

Answer 1

我在Linux机器上遇到了同样的问题,并查看了提升asio文档.您只需要向query构造函数添加一个flag参数: tcp::resolver::query query("localhost","10127",tcp::resolver::query::canonical_name);

注意:完整范围的名称query是boost::asio::ip::tcp::resolver::query.

发生这种情况是因为此处传递的默认flags参数是boost::asio::ip::tcp::resolver::query::address_configured,这意味着如果为系统配置了非环回IPv4/IPv6地址,则调用应仅解析IPv4/IPv6地址.

Answer 2

I have no explanation of why you have this error. However, what I did in a project was not by specifying the port number directly, but rather by constructing the endpoint instance in two steps. I don't recall the rationale at the time for doing it this way, but it might help you.

我提出的解决方案是这样的：

ip::tcp::resolver::query query(ip::tcp::v4(), "localhost", ""); // empty service name
tcp::resolver::iterator it_endpoint = resolver.resolve(query);
ip::tcp::endpoint endpoint(ip::tcp::endpoint(*it_endpoint).address(), port);

这是我所做的总结摘录，因此它可能无法按原样编译。