程序运行截图如下：

原理（原理和爬虫一样）：

1.伪造HTTP数据封包头

2.处理爬下来的网站

关键代码如下：

inquireip.h

#ifndef INQUIREIP_H
#define INQUIREIP_H

#include <QObject>
#include <QTcpSocket>

class InquireIp : public QObject
{
    Q_OBJECT
public:
    explicit InquireIp(QObject *parent = 0);
    void startConnect(const QString host,quint16 port);
    void setIp(const QString ip);

public slots:
    void onConnected();
    void onReadyRead();

signals:
    void sendIpLocation(QString msg);

protected:
    void disposeHTTPContent(QString msg);

private:
    QTcpSocket *m_socket;
    QString m_ip;
    QString m_httpContent;
};

#endif // INQUIREIP_H

inquireip.cpp

#include "inquireip.h"
#include <QDebug>
#include <QTextCodec>
#include <QByteArray>

InquireIp::InquireIp(QObject *parent) :
    QObject(parent),m_socket(0),m_ip("")
{
    m_ip="127.0.0.1";
}

void InquireIp::startConnect(const QString host, quint16 port)
{
    m_socket=new QTcpSocket(this);
    connect(m_socket,SIGNAL(connected()),this,SLOT(onConnected()));
    connect(m_socket,SIGNAL(readyRead()),this,SLOT(onReadyRead()));
    m_socket->connectToHost(host,port);
}

void InquireIp::setIp(const QString ip)
{
    m_ip=ip;
}

void InquireIp::onConnected(){

    QString msg=QString("GET /ips138.asp?ip=%1&action=2 HTTP/1.1\r\n"
                 "Host: www.ip138.com\r\n"
                 "User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0\r\n"
                 "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n"
                 "Accept-Language: zh-CN,zh;q=0.8,en-US;q=0.5,en;q=0.3\r\n"
                 "Accept-Encoding: gzip, deflate\r\n"
                 "Referer: http://www.ip138.com/\r\n"
                 "Cookie: pgv_pvi=1815538688; pgv_si=s3422986240; ASPSESSIONIDCASTDCQB=CNPDBLMDPKKBEFLKKAMALGIK; ASPSESSIONIDQACDQCBR=DOAMDOGDCEGHLCPBBOIHKHFI\r\n"
                 "Connection: keep-alive\r\n"
                 "Upgrade-Insecure-Requests: 1\r\n\r\n").arg(m_ip);

    m_socket->write(msg.toLatin1());

}

void InquireIp::onReadyRead()
{
    QTextCodec *codec = QTextCodec::codecForName("gb2312");
    QString qstr = codec->toUnicode(m_socket->readAll());
    int q1=qstr.indexOf("<li>");
    int q2=qstr.indexOf("</li>");
    QString str=qstr.mid(q1+9,q2-q1);
    QStringList strList=str.split(" ");
    if(strList[0]=="")
        return;

    emit sendIpLocation(strList[0]);
}

void InquireIp::disposeHTTPContent(QString msg)
{

}