When I try to connect to 192.168.2.71

connectToHost( host, port );
if ( !waitForConnected( connectionTimeout ) )
{
    qDebug() << QAbstractSocket::error() << errorString();
    ...
}

I get an error:

QAbstractSocket::UnsupportedSocketOperationError "The proxy type is invalid for this operation"

While my proxy setting are:

So proxy should not be applied as it's a local address + 192.168.2.* is in exceptions.

Notes:

1) disabling system proxy solves the issue

2) setProxy( QNetworkProxy::NoProxy **) solves the problem

3) connection to 127.0.0.1 does not have this issue (though it's the same computer as 192.168.2.71)