直接调用就行：

.returnOutIP()；这个方法返回的就是外网IP了~

引用头：

#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QEventLoop>

调用：

QString TcpSever::returnOutIP()
{
    return GetNetIP(GetHtml("http://2017.ip138.com/ic.asp"));
}
私有：
QString TcpSever::GetHtml(QString url)
{
    QNetworkAccessManager *manager = new QNetworkAccessManager();
    QNetworkReply *reply = manager->get(QNetworkRequest(QUrl(url)));
    QByteArray responseData;
    QEventLoop eventLoop;
    QObject::connect(manager, SIGNAL(finished(QNetworkReply *)), &eventLoop, SLOT(quit()));
    eventLoop.exec();
    responseData = reply->readAll();
    return QString(responseData);
}
QString TcpSever::GetNetIP(QString webCode)
{    
    QString tmp = webCode.split("[").last();
    return tmp.split("]").first();
}