winrt: Use hostnames for socket connections

Using IP addresses does not work for every use case on WinRT. The
workaround that is in place for VPN connections uses the host name
directly but has the disadvantage that it:
    1) does a host lookup nevertheless and ends up using the host name
    afterwards.
    2) needs a set environment variable to be activated.

Instead of doing a host lookup we now use the same approach that is used
if a proxy with the HostNameLookupCapability is present. In this case the
lookup is skipped and the direction is made using the hostname.

The big advantage of hostname over ip addresses on WinRt is, that
Windows handles everything related to lookup and proxies (it uses the
system proxy in this case), so we do not have to take care of that.
As the WinRT backend falls back to the "connectToHostByName" in any
case no further adaptions are needed.

QT_WINRT_USE_THREAD_NETWORK_CONTEXT cannot be completely removed though
as the creation of the network context should not be done
unconditionally.

This change partially reverts e9fa435652ef064515bd5c04c0b5e5c4a30ebca4

Task-number: QTBUG-59989
Change-Id: I5dc7481b7499192641470b4b5a6642509a4b4f38
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>

1 files changed, 8 insertions, 5 deletions

diff --git a/src/network/socket/qabstractsocket.cpp b/src/network/socket/qabstractsocket.cpp
index 7ecbf35489..9cb6c4be57 100644
--- a/src/network/socket/qabstractsocket.cpp
+++ b/src/network/socket/qabstractsocket.cpp
@@ -943,7 +943,9 @@ void QAbstractSocketPrivate::resolveProxy(const QString &hostname, quint16 port)
     // DefaultProxy here will raise an error
     proxyInUse = QNetworkProxy();
 }
+#endif // !QT_NO_NETWORKPROXY
 
+#if !defined(QT_NO_NETWORKPROXY) || defined(Q_OS_WINRT)
 /*!
     \internal
 
@@ -981,7 +983,7 @@ void QAbstractSocketPrivate::startConnectingByName(const QString &host)
     emit q->stateChanged(state);
 }
 
-#endif
+#endif // !QT_NO_NETWORKPROXY || Q_OS_WINRT
 
 /*! \internal
 
@@ -1113,10 +1115,6 @@ void QAbstractSocketPrivate::_q_connectToNextAddress()
         // (localhost address on BSD or any UDP connect), emit
         // connected() and return.
         if (
-#if defined(Q_OS_WINRT) && _MSC_VER >= 1900
-            !qEnvironmentVariableIsEmpty("QT_WINRT_USE_THREAD_NETWORK_CONTEXT") ?
-                socketEngine->connectToHostByName(hostName, port) :
-#endif
             socketEngine->connectToHost(host, port)) {
                 //_q_testConnection();
                 fetchConnectionParameters();
@@ -1712,6 +1710,7 @@ void QAbstractSocket::connectToHost(const QString &hostName, quint16 port,
     QIODevice::open(openMode);
     d->readChannelCount = d->writeChannelCount = 0;
 
+#ifndef Q_OS_WINRT
     d->state = HostLookupState;
     emit stateChanged(d->state);
 
@@ -1749,6 +1748,10 @@ void QAbstractSocket::connectToHost(const QString &hostName, quint16 port,
            (d->state == ConnectingState || d->state == HostLookupState)
            ? " (connection in progress)" : "");
 #endif
+#else // !Q_OS_WINRT
+    // On WinRT we should always connect by name. Lookup and proxy handling are done by the API.
+    d->startConnectingByName(hostName);
+#endif
 }
 
 /*! \overload