c++ - Qt4 DNS 代理 QUdpSocket

Question

我实际上是在尝试使用 Qt4 制作 DNS 代理应用程序。如果我将 DNS 名称服务器设置为“localhost”，那么我想将所有 DNS 请求转发到 remoteSocket 对象中指定的服务器。除了将数据从 remoteSocket 对象发送回请求 DNS 查找的 localSocket 对象外，一切似乎都工作正常。

在写入 localSocket 时，我需要了解什么具体信息吗？问题似乎出在 readResponse() 中。

#include "dns.h"

Dns::Dns()
{
}

void Dns::initSocket()
{
    localDatagram = new QByteArray();
    remoteDatagram = new QByteArray();

    localSocket = new QUdpSocket();
    connect(localSocket, SIGNAL(readyRead()), this, SLOT(readRequest()), Qt::DirectConnection);
    localSocket->bind(QHostAddress::LocalHost, 53);

    remoteSocket = new QUdpSocket();
    remoteSocket->connectToHost(QHostAddress("4.2.2.1"), 53);
    connect(remoteSocket, SIGNAL(readyRead()), this, SLOT(readResponse()), Qt::DirectConnection);

}

void Dns::readRequest()
{
    while (localSocket->hasPendingDatagrams()) {
        localDatagram->resize(localSocket->pendingDatagramSize());\
        localSocket->readDatagram(localDatagram->data(), localDatagram->size());
        remoteSocket->write(*localDatagram);
    }
}

void Dns::readResponse()
{
    QByteArray bytes(remoteSocket->readAll());
    qDebug() << "BYTES: [" << bytes.toBase64() << "]";
    localSocket->write(bytes);
}

Answer 1

我假设使用 QUdpSocket::bind()，生成的套接字对象将能够使用访问方法获得 peerAddress/peerPort，但事实并非如此。

最终的解决方案是:

QHostAddress sender;
quint16 senderPort;

localSocket->readDatagram(localDatagram->data(), localDatagram->size(), &sender, &senderPort);

并且在 readResponse() 中，

localSocket->writeDatagram(bytes, sender, senderPort);