如何检查网络地址是否在Qt本地 [英] How to check if network address is local in Qt
问题描述
我想知道网络地址(名称或IP)是否指向远程服务器或本地计算机。我可以使用 QHostInfo
来查找IP地址,但在这种情况下,我必须等待DNS服务器的响应。我不想知道服务器的IP地址,我只需要检查它是否是本地的。
I want to know if network address (name or IP) points to remote server or local machine. I can use QHostInfo
to lookup IP address, but in this case I would have to wait for DNS server's response. I don't want to know server's IP address, I only need to check if it is local or not. Is there any faster way to check this?
推荐答案
我可以使用
QHostInfo
来查找IP地址,但在这种情况下,我将不得不等待DNS服务器的响应。
I can use
QHostInfo
to lookup IP address, but in this case I would have to wait for DNS server's response.
QHostInfo
使用特定于平台的名称解析机制。它可能不使用DNS。如果本地接口的主机名在hosts文件中,并且名称解析被配置为使用它,则 QHostInfo
将以这种方式解析本地接口的地址。
QHostInfo
uses the platform-specific name resolution mechanism. It might not use DNS at all. If the hostname of a local interface is in the hosts file, and the name resolution is configured to use it, then QHostInfo
will resolve the local interface's address that way. Otherwise, it'll do a name server query, iff the platform is configured to resolve names that way.
你可以做的最多的是检查 QHostAddress :: isLoopback()
,然后检查它是否为 QNetworkInterface :: allAddresses()
。
The most you can do is to check QHostAddress::isLoopback()
, then check if it's one of QNetworkInterface::allAddresses()
.
如果您的地址不是IP地址,并且不等于 QHostInfo :: localHostName()
,那么您必须先使用 QHostInfo :: lookupHost
。如果它是本地接口的名称,列出在hosts文件或类似的本地解析机制,它会被快速返回。你可以设置一个短暂的超时(比如100ms),如果那时没有可用的查找结果,你可以假设它不是一个本地接口。
If your address is not an IP address, and it's not equal to QHostInfo::localHostName()
, then you have to obtain one first using QHostInfo::lookupHost
. If it's a local interface's name, listed in the hosts file or a similar local resolution mechanism, it will be returned quickly. You can set a short timeout (say 100ms), and if there's no lookup result available by then, you can assume that it's not a local interface.
// https://github.com/KubaO/stackoverflown/tree/master/questions/host-lookup-36319049
#include <QtWidgets>
#include <QtNetwork>
class IfLookup : public QObject {
Q_OBJECT
int m_id;
QTimer m_timer;
void abort() {
if (m_timer.isActive())
QHostInfo::abortHostLookup(m_id);
m_timer.stop();
}
Q_SLOT void lookupResult(const QHostInfo & host) {
m_timer.stop();
if (host.error() != QHostInfo::NoError)
return hasResult(Error);
for (auto ifAddr : QNetworkInterface::allAddresses())
if (host.addresses().contains(ifAddr))
return hasResult(Local);
return hasResult(NonLocal);
}
public:
enum Result { Local, NonLocal, TimedOut, Error };
IfLookup(QObject * parent = 0) : QObject(parent) {
connect(&m_timer, &QTimer::timeout, this, [this]{
abort();
emit hasResult(TimedOut);
});
}
Q_SIGNAL void hasResult(Result);
Q_SLOT void lookup(QString name) {
abort();
name = name.trimmed().toUpper();
QHostAddress addr(name);
if (!addr.isNull()) {
if (addr.isLoopback() || QNetworkInterface::allAddresses().contains(addr))
return hasResult(Local);
return hasResult(NonLocal);
}
if (QHostInfo::localHostName() == name)
return hasResult(Local);
m_id = QHostInfo::lookupHost(name, this, SLOT(lookupResult(QHostInfo)));
m_timer.start(500);
}
};
int main(int argc, char ** argv) {
QApplication app{argc, argv};
QWidget w;
QFormLayout layout{&w};
QLineEdit address;
layout.addRow("Address to look up", &address);
QLabel result;
layout.addRow("Result", &result);
QPushButton lookup{"Lookup"};
layout.addRow(&lookup);
lookup.setDefault(true);
w.show();
IfLookup ifLookup;
QObject::connect(&lookup, &QPushButton::clicked, [&]{
result.clear();
ifLookup.lookup(address.text());
});
QObject::connect(&ifLookup, &IfLookup::hasResult, [&](IfLookup::Result r){
static const QMap<IfLookup::Result, QString> msgs = {
{ IfLookup::Local, "Local" }, { IfLookup::NonLocal, "Non-Local" },
{ IfLookup::TimedOut, "Timed Out" }, { IfLookup::Error, "Lookup Error" }
};
result.setText(msgs.value(r));
});
return app.exec();
}
#include "main.moc"
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