Does Qt provide a class that represents an IP address?

Question

I thought QHostAddress was it, but it strangely does not provide methods for validating whether or not the IP address is valid (anymore, got deprecated to Qt3).

Does anyone know?

Answer 1

There is an alternative to using isIpv4Address() and isIPv6Address(). For example:

QHostAddress address(myString);
if (QAbstractSocket::IPv4Protocol == address.protocol())
{
   qDebug("Valid IPv4 address.");
}
else if (QAbstractSocket::IPv6Protocol == address.protocol())
{
   qDebug("Valid IPv6 address.");
}
else
{
   qDebug("Unknown or invalid address.");
}

See also:

http://doc.qt.digia.com/4.6/qhostaddress.html#protocol

Hope this helps.

Answer 2

Here is the official answer from Nokia support engineer, name removed for privacy protection:

I posted a question on stackoverflow.com as follow:

Does Qt provide a class that represents an IP address?

You can see that someone posted a solution to my question already.

However, I want to ask how come Nokia doesn't just provide a method to

QHostAddress ( like isValid() ) that will check the host address's validity?

Thank you for your inquiry. You can use the isNull() method to check the validity. It will return true for invalid addresses: http://doc.qt.digia.com/4.6/qhostaddress.html#isNull

Hope this helps.

Regards,

Support Engineer, Qt Development Frameworks, Nokia

Answer 3

The bool return value of QHostAddress::setAddress(const QString &address) tells if the string is successfully parsed as an IPv4 or IPv6 address.

QHostAddress addr;
if (addr.setAddress(myString)) {
    // valid
} else {
    // invalid
}

http://doc.qt.io/qt-5/qhostaddress.html#setAddress-5

Answer 4

I found all of the above solutions to be unreliable for IPv4 addresses at least. For example when '192' and '192.' were used to create a QHostAddress. Both .setAddress() and if(QAbstractSocket::IPv4Protocol == address.protocol() returned true!

I found a more robust solution is to check the IP address string format using QRegularExpression and QRegularExpressionValidator.

An example of a good IPv4 regular expression can be found here

How to set Input Mask and QValidator to a QLineEdit at a time in Qt?