前面分析中，一个问题一直没有解决：新生成的SOCKET是什么时候加入WSASelect()的？另外还有一个不是很大的问题，close流程。
在QEventDispatcherWin32Private::doWsaAsyncSelect()中WSAAsyncSelect()设置一个断点，观察call stack:
> QtCored4.dll!QEventDispatcherWin32Private::doWsaAsyncSelect(int socket=0x00001628) 行633 C++
QtCored4.dll!QEventDispatcherWin32::registerSocketNotifier(QSocketNotifier * notifier=0x00c6f248) 行829 C++
QtCored4.dll!QSocketNotifier::QSocketNotifier(int socket=0x00001628, QSocketNotifier::Type type=Write, QObject * parent=0x00c66228) 行185 C++
QtNetworkd4.dll!QWriteNotifier::QWriteNotifier(int fd=0x00001628, QNativeSocketEngine * parent=0x00c66228) 行1053 + 0x1a 字节 C++
QtNetworkd4.dll!QNativeSocketEngine::setWriteNotificationEnabled(bool enable=true) 行1118 + 0x2d 字节 C++
QtNetworkd4.dll!QAbstractSocketPrivate::_q_connectToNextAddress() 行996 C++
QtNetworkd4.dll!QAbstractSocketPrivate::_q_startConnecting(const QHostInfo & hostInfo={...}) 行890 C++
QtNetworkd4.dll!QAbstractSocket::qt_metacall(QMetaObject::Call _c=InvokeMetaMethod, int _id=0x0000000a, void * * _a=0x00c6e510) 行104 + 0x16 字节 C++
QtNetworkd4.dll!QTcpSocket::qt_metacall(QMetaObject::Call _c=InvokeMetaMethod, int _id=0x00000012, void * * _a=0x00c6e510) 行58 + 0x14 字节 C++
QtCored4.dll!QMetaCallEvent::placeMetaCall(QObject * object=0x00c4f790) 行478 C++
QtCored4.dll!QObject::event(QEvent * e=0x00c4d8a0) 行1102 + 0x14 字节 C++
QtGuid4.dll!QApplicationPrivate::notify_helper(QObject * receiver=0x00c4f790, QEvent * e=0x00c4d8a0) 行4065 + 0x11 字节 C++
QtGuid4.dll!QApplication::notify(QObject * receiver=0x00c4f790, QEvent * e=0x00c4d8a0) 行3605 + 0x10 字节 C++
QtCored4.dll!QCoreApplication::notifyInternal(QObject * receiver=0x00c4f790, QEvent * event=0x00c4d8a0) 行610 + 0x15 字节 C++
QtCored4.dll!QCoreApplication::sendEvent(QObject * receiver=0x00c4f790, QEvent * event=0x00c4d8a0) 行213 + 0x39 字节 C++
QtCored4.dll!QCoreApplicationPrivate::sendPostedEvents(QObject * receiver=0x00000000, int event_type=0x00000000, QThreadData * data=0x00bc8890) 行1247 + 0xd 字节 C++
QtCored4.dll!QEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行679 + 0x10 字节 C++
QtGuid4.dll!QGuiEventDispatcherWin32::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行1182 + 0x15 字节 C++
QtCored4.dll!QEventLoop::processEvents(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行150 C++
QtCored4.dll!QEventLoop::exec(QFlags<enum QEventLoop::ProcessEventsFlag> flags={...}) 行201 + 0x2d 字节 C++
QtGuid4.dll!QDialog::exec() 行499 C++
fortuneclient.exe!main(int argc=0x00000001, char * * argv=0x00bc8750) 行51 + 0x9 字节 C++
fortuneclient.exe!WinMain(HINSTANCE__ * instance=0x00400000, HINSTANCE__ * prevInstance=0x00000000, char * __formal=0x001520e2, int cmdShow=0x00000001) 行137 + 0x12 字节 C++
fortuneclient.exe!__tmainCRTStartup() 行574 + 0x35 字节 C
fortuneclient.exe!WinMainCRTStartup() 行399 C
kernel32.dll!7c82f23b()
[下面的框架可能不正确和/或缺失，没有为 kernel32.dll 加载符号]
看QNativeSocketEngine::setWriteNotificationEnabled()的代码实现：
void QNativeSocketEngine::setWriteNotificationEnabled(bool enable)
{
Q_D(QNativeSocketEngine);
if (d->writeNotifier) {
d->writeNotifier->setEnabled(enable);
} else if (enable && d->threadData->eventDispatcher) {
d->writeNotifier = new QWriteNotifier(d->socketDescriptor, this);
d->writeNotifier->setEnabled(true);
}
}
在QWriteNotifier对象新建的时候，引起其父类的构建：QSocketNotifier
QSocketNotifier::QSocketNotifier(int socket, Type type, QObject *parent)
: QObject(parent)
{
if (socket < 0)
qWarning("QSocketNotifier: Invalid socket specified");
sockfd = socket;
sntype = type;
snenabled = true;
Q_D(QObject);
if (!d->threadData->eventDispatcher) {
qWarning("QSocketNotifier: Can only be used with threads started with QThread");
} else {
d->threadData->eventDispatcher->registerSocketNotifier(this);
}
}
原来是通过获取当前线程数据得到Dispatcher的指针（QEventDispatcherWin32），通过其注册QNativeSocketEngine对象自己本身。
void QEventDispatcherWin32::registerSocketNotifier(QSocketNotifier *notifier)
{
Q_ASSERT(notifier);
int sockfd = notifier->socket();
int type = notifier->type();
Q_D(QEventDispatcherWin32);
QSNDict *sn_vec[3] = { &d->sn_read, &d->sn_write, &d->sn_except };
QSNDict *dict = sn_vec[type];
if (QCoreApplication::closingDown()) // ### d->exitloop?
return; // after sn_cleanup, don't reinitialize.
if (dict->contains(sockfd)) {
const char *t[] = { "Read", "Write", "Exception" };
/* Variable "socket" below is a function pointer. */
qWarning("QSocketNotifier: Multiple socket notifiers for "
"same socket %d and type %s", sockfd, t[type]);
}
QSockNot *sn = new QSockNot;
sn->obj = notifier;
sn->fd = sockfd;
dict->insert(sn->fd, sn);
if (d->internalHwnd)
d->doWsaAsyncSelect(sockfd);
}
在这里跟前面分析的QEventDispatcherWin32消息处理搭上关系了，把QWriteNotifier对象加入到系统的列表中；在QApplication::exec()的消息循环中，就能够获取目标对象了。