Qt深度分析之《网络编程详解(1)》
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首先对Windows下的网络编程总结一下：
如果是服务器，其WinSDK调用分别为：
WSAStartup() -> socket() -> htons() / htonl() -> bind() -> listen() -> accept() -> recv() / send() -> closesocket() -> WSACleanup()如果是客户端程序，其调用序列为：
WSAStartup() -> socket() -> htons() / htonl() -> connect() -> recv() / send() -> closesocket() -> WSACleanup()前面转贴的客户端（WinSocket温习）程序中，收到信息就在console打印出来然后退出了；在一般的应用中，通常是要一直等待收发消息的，直到程序确认退出才关闭socket。如果用一个轮询就会占用很多的CPU资源，所以很多嵌入式设计中会用一个WaitForMultiObject调用，等待退出命令或者超时，然后退出或进行下一轮信息接受。在Windows平台下也有一些比较高明的设计，使用异步socket，然后用异步选择的办法，实现多线程和事件的并发。在WinSocket中，同样也有一套异步Socket函数，那就是使用WSAAsyncSelect()及其配合函数。具体可以参考MSDN。QT在Windows平台上的实现，肯定也跟这些SDK调用有关。
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按照这个思路，果然在QT代码里面找到了Qnativesocketengine_win.cpp，WSAStartup()，WSASocket()等序列WSA函数都有。QNativeSocketEnginePrivate类把这些SDK封装成：createNewSocket()、option()、setOption()、nativeConnect()、nativeBind()、nativeListen()、nativeAccept()、nativeWrite()、nativeRead()、nativeSelect()、nativeClose()等。按照QT的设计，QPrivate类是数据类；Q类应该是主类。接着看QNativeSocket类的继承：
QNativeSocketEngine : public QAbstractSocketEngine : public QObjectQAbstractSocketEngine类是使用了大量纯虚函数的定义。继续深入查看，发现大量有关的类：QAbstractSocket，SocketAsyncHandler，QTcpSocket，QUdpSocket等，看来我要先了解下QT网络编程体系再进一步分析之：
之前没有看QT自带的文档，看了doc之后对QT的网络体系有一个大致的了解：
QNatvieSocketEnginePrivate是OS相关的API封装，和QNativeSocketEngine一起构成具体平台SOCKET实现；
QTcpSocket、QUdpSocket、QTcpServer构成底层的应用API；QSslSocket是SSL加密相关API；
QHttp、QFtp构成高层次应该API；
QNetworkAccessManager、QNetworkRequest、QNetworkReply是高度抽象的网络层。
分析TCP的例子fortuneclient，运行起来按了[Get
Fortune]按钮之后，调用的是Client::requestNewFortune()。
void Client::requestNewFortune()
getFortuneButton->setEnabled(false);
blockSize = 0;
tcpSocket->abort();
tcpSocket->connectToHost(hostLineEdit->text(), portLineEdit->text().toInt());
}具体看QTcpSocket::connectToHost()的代码
void QAbstractSocket::connectToHost(const QString &hostName, quint16 port,
OpenMode openMode)
QMetaObject::invokeMethod(this, "connectToHostImplementation",
Qt::DirectConnection,
Q_ARG(QString, hostName),
Q_ARG(quint16, port),
Q_ARG(OpenMode, openMode));
}调用的是QAbstractSocket::connectToHostImplementation()。
void QAbstractSocket::connectToHostImplementation(const QString &hostName, quint16 port,
OpenMode openMode)
Q_D(QAbstractSocket);
if (d->state == ConnectedState || d->state == ConnectingState || d->state == ClosingState) {
qWarning("QAbstractSocket::connectToHost() called when already connecting/connected to \"%s\"", qPrintable(hostName));
return;
d->hostName = hostName;
d->port = port;
d->state = UnconnectedState;
d->readBuffer.clear();
d->writeBuffer.clear();
d->abortCalled = false;
d->closeCalled = false;
d->pendingClose = false;
d->localPort = 0;
d->peerPort = 0;
d->localAddress.clear();
d->peerAddress.clear();
d->peerName = hostName;
if (d->hostLookupId != -1) {
QHostInfo::abortHostLookup(d->hostLookupId);
d->hostLookupId = -1;
#ifndef QT_NO_NETWORKPROXY
// Get the proxy information
d->resolveProxy(hostName, port);
if (d->proxyInUse.type() == QNetworkProxy::DefaultProxy) {
// failed to setup the proxy
d->socketError = QAbstractSocket::UnsupportedSocketOperationError;
setErrorString(QAbstractSocket::tr("Operation on socket is not supported"));
emit error(d->socketError);
return;
#endif
if (!d_func()->isBuffered)
openMode |= QAbstractSocket::Unbuffered;
QIODevice::open(openMode); // ？？
d->state = HostLookupState;
emit stateChanged(d->state);
QHostAddress temp;
if (temp.setAddress(hostName)) {
QHostInfo info;
info.setAddresses(QList<QHostAddress>() << temp);
d->_q_startConnecting(info);
#ifndef QT_NO_NETWORKPROXY
} else if (d->proxyInUse.capabilities() & QNetworkProxy::HostNameLookupCapability) {
// the proxy supports connection by name, so use it
d->startConnectingByName(hostName);
return;
#endif
} else {
if (d->threadData->eventDispatcher)
d->hostLookupId = QHostInfo::lookupHost(hostName, this, SLOT(_q_startConnecting(QHostInfo)));
}继续调用QAbstractSocket::_q_startConnecting()，是QAbstractSocket的私有信号。简单来说，_q_startConnecting()就是调用了_q_connectToNextAddress()而已。
void QAbstractSocketPrivate::_q_connectToNextAddress()
Q_Q(QAbstractSocket);
// Check for more pending addresses
if (addresses.isEmpty()) {
state = QAbstractSocket::UnconnectedState;
if (socketEngine) {
if ((socketEngine->error() == QAbstractSocket::UnknownSocketError
) && socketEngine->state() == QAbstractSocket::ConnectingState) {
socketError = QAbstractSocket::ConnectionRefusedError;
q->setErrorString(QAbstractSocket::tr("Connection refused"));
} else {
socketError = socketEngine->error();
q->setErrorString(socketEngine->errorString());
} else {
// socketError = QAbstractSocket::ConnectionRefusedError;
// q->setErrorString(QAbstractSocket::tr("Connection refused"));
emit q->stateChanged(state);
emit q->error(socketError);
return;
// Pick the first host address candidate
host = addresses.takeFirst();
#if defined(QT_NO_IPV6)
if (host.protocol() == QAbstractSocket::IPv6Protocol) {
// If we have no IPv6 support, then we will not be able to
// connect. So we just pretend we didn't see this address.
continue;
#endif
if (!initSocketLayer(host.protocol())) {
// hope that the next address is better
continue;
// Tries to connect to the address. If it succeeds immediately
// (localhost address on BSD or any UDP connect), emit
// connected() and return.
if (socketEngine->connectToHost(host, port)) {
//_q_testConnection();
fetchConnectionParameters();
return;
// cache the socket descriptor even if we're not fully connected yet
cachedSocketDescriptor = socketEngine->socketDescriptor();
// Check that we're in delayed connection state. If not, try
// the next address
if (socketEngine->state() != QAbstractSocket::ConnectingState) {
continue;
// Start the connect timer.
if (threadData->eventDispatcher) {
if (!connectTimer) {
connectTimer = new QTimer(q);
QObject::connect(connectTimer, SIGNAL(timeout()),
q, SLOT(_q_abortConnectionAttempt()),
Qt::DirectConnection);
connectTimer->start(QT_CONNECT_TIMEOUT);
// Wait for a write notification that will eventually call
// _q_testConnection().
socketEngine->setWriteNotificationEnabled(true);
break;
} while (state != QAbstractSocket::ConnectedState);
}上面关键的三句，实际是把WinSocket编程中的简单过程分成三个阶段：socket初始化；connect到远程目标；设定Timer定时查看并处理Select的情况（收发数据或者关闭socket）。这里主要看前面两个：初始化和连接，select的处理放到明天分析。
1、初始化
bool QAbstractSocketPrivate::initSocketLayer(QAbstractSocket::NetworkLayerProtocol protocol)
#ifdef QT_NO_NETWORKPROXY
// this is here to avoid a duplication of the call to createSocketEngine below
static const QNetworkProxy &proxyInUse = *(QNetworkProxy *)0;
#endif
Q_Q(QAbstractSocket);
resetSocketLayer();
socketEngine = QAbstractSocketEngine::createSocketEngine(q->socketType(), proxyInUse, q);
if (!socketEngine) {
socketError = QAbstractSocket::UnsupportedSocketOperationError;
q->setErrorString(QAbstractSocket::tr("Operation on socket is not supported"));
return false;
if (!socketEngine->initialize(q->socketType(), protocol)) {
socketError = socketEngine->error();
q->setErrorString(socketEngine->errorString());
return false;
if (threadData->eventDispatcher)
socketEngine->setReceiver(this);
return true;
QAbstractSocketEngine *QAbstractSocketEngine::createSocketEngine(QAbstractSocket::SocketType socketType, const QNetworkProxy &proxy, QObject *parent)
#ifndef QT_NO_NETWORKPROXY
// proxy type must have been resolved by now
if (proxy.type() == QNetworkProxy::DefaultProxy)
return 0;
#endif
QMutexLocker locker(&socketHandlers()->mutex);
for (int i = 0; i < socketHandlers()->size(); i++) {
if (QAbstractSocketEngine *ret = socketHandlers()->at(i)->createSocketEngine(socketType, proxy, parent))
return ret;
return new QNativeSocketEngine(parent);
}上面可以知道 socketEngine->initialize()实际调用的是QNativeSocketEngine::initialize()
bool QNativeSocketEngine::initialize(QAbstractSocket::SocketType socketType, QAbstractSocket::NetworkLayerProtocol protocol)
Q_D(QNativeSocketEngine);
if (isValid())
close();
#if defined(QT_NO_IPV6)
if (protocol == QAbstractSocket::IPv6Protocol) {
d->setError(QAbstractSocket::UnsupportedSocketOperationError,
QNativeSocketEnginePrivate::NoIpV6ErrorString);
return false;
#endif
// Create the socket
if (!d->createNewSocket(socketType, protocol)) {
return false;
// Make the socket nonblocking.
if (!setOption(NonBlockingSocketOption, 1)) {
d->setError(QAbstractSocket::UnsupportedSocketOperationError,
QNativeSocketEnginePrivate::NonBlockingInitFailedErrorString);
close();
return false;
// Set the broadcasting flag if it's a UDP socket.
if (socketType == QAbstractSocket::UdpSocket
&& !setOption(BroadcastSocketOption, 1)) {
d->setError(QAbstractSocket::UnsupportedSocketOperationError,
QNativeSocketEnginePrivate::BroadcastingInitFailedErrorString);
close();
return false;
// Make sure we receive out-of-band data
if (socketType == QAbstractSocket::TcpSocket
&& !setOption(ReceiveOutOfBandData, 1)) {
qWarning("QNativeSocketEngine::initialize unable to inline out-of-band data");
// Set the send and receive buffer sizes to a magic size, found
// most optimal for our platforms.
setReceiveBufferSize(49152);
setSendBufferSize(49152);
d->socketType = socketType;
d->socketProtocol = protocol;
return true;
}至此，初始化过程完成，socket被设定为非阻塞模式（也就是Select会超时方式）。
2、connect到远程目标
bool QNativeSocketEngine::connectToHost(const QHostAddress &address, quint16 port)
Q_D(QNativeSocketEngine);
Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::connectToHost(), false);
#if defined (QT_NO_IPV6)
if (address.protocol() == QAbstractSocket::IPv6Protocol) {
d->setError(QAbstractSocket::UnsupportedSocketOperationError,
QNativeSocketEnginePrivate::NoIpV6ErrorString);
return false;
#endif
if (!d->checkProxy(address))
return false;
Q_CHECK_STATES(QNativeSocketEngine::connectToHost(),
QAbstractSocket::UnconnectedState, QAbstractSocket::ConnectingState, false);
d->peerAddress = address;
d->peerPort = port;
bool connected = d->nativeConnect(address, port);
if (connected)
d->fetchConnectionParameters();
return connected;
}连接相对简单。
3、读取信息
在QAbstractSocket中，有两个成员是收发数据用的：readData()、writeData()
readData()有两种读取方式：有缓冲和无缓冲方式。基本原理是一致的，简单其见只分析无缓冲直接读取方式。
qint64 QAbstractSocket::readData(char *data, qint64 maxSize)
Q_D(QAbstractSocket);
if (d->socketEngine && !d->socketEngine->isReadNotificationEnabled() && d->socketEngine->isValid())
d->socketEngine->setReadNotificationEnabled(true);
if (!d->isBuffered) {
if (!d->socketEngine)
return -1; // no socket engine is probably EOF
qint64 readBytes = d->socketEngine->read(data, maxSize);
if (readBytes < 0) {
d->socketError = d->socketEngine->error();
setErrorString(d->socketEngine->errorString());
if (!d->socketEngine->isReadNotificationEnabled())
d->socketEngine->setReadNotificationEnabled(true);
return readBytes;
if (d->readBuffer.isEmpty())
// if we're still connected, return 0 indicating there may be more data in the future
// if we're not connected, return -1 indicating EOF
return d->state == QAbstractSocket::ConnectedState ? qint64(0) : qint64(-1);
// If readFromSocket() read data, copy it to its destination.
if (maxSize == 1) {
*data = d->readBuffer.getChar();
return 1;
qint64 bytesToRead = qMin(qint64(d->readBuffer.size()), maxSize);
qint64 readSoFar = 0;
while (readSoFar < bytesToRead) {
const char *ptr = d->readBuffer.readPointer();
int bytesToReadFromThisBlock = qMin(int(bytesToRead - readSoFar),
d->readBuffer.nextDataBlockSize());
memcpy(data + readSoFar, ptr, bytesToReadFromThisBlock);
readSoFar += bytesToReadFromThisBlock;
d->readBuffer.free(bytesToReadFromThisBlock);
return readSoFar;
}从前面（二）可以知道，socketEngine->read()实际调用的是QNativeSocketEngine::read()
qint64 QNativeSocketEngine::read(char *data, qint64 maxSize)
Q_D(QNativeSocketEngine);
Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::read(), -1);
Q_CHECK_STATES(QNativeSocketEngine::read(), QAbstractSocket::ConnectedState, QAbstractSocket::BoundState, -1);
qint64 readBytes = d->nativeRead(data, maxSize);
// Handle remote close
if (readBytes == 0 && d->socketType == QAbstractSocket::TcpSocket) {
d->setError(QAbstractSocket::RemoteHostClosedError,
QNativeSocketEnginePrivate::RemoteHostClosedErrorString);
close();
return -1;
return readBytes;
}除了一些相关的检查，就是调用QNativeSocketPrivate::nativeRead()
qint64 QNativeSocketEnginePrivate::nativeRead(char *data, qint64 maxLength)
qint64 ret = -1;
WSABUF buf;
buf.buf = data;
buf.len = maxLength;
DWORD flags = 0;
DWORD bytesRead = 0;
#if defined(Q_OS_WINCE)
WSASetLastError(0);
#endif
if (::WSARecv(socketDescriptor, &buf, 1, &bytesRead, &flags, 0,0) == SOCKET_ERROR) {
int err = WSAGetLastError();
WS_ERROR_DEBUG(err);
switch (err) {
case WSAEWOULDBLOCK:
ret = -2;
break;
case WSAEBADF:
case WSAEINVAL:
setError(QAbstractSocket::NetworkError, ReadErrorString);
break;
case WSAECONNRESET:
case WSAECONNABORTED:
// for tcp sockets this will be handled in QNativeSocketEngine::read
ret = 0;
break;
default:
break;
} else {
if (WSAGetLastError() == WSAEWOULDBLOCK)
ret = -2;
ret = qint64(bytesRead);
return ret;
}至此，调用Windows API读取数据。
4、发送数据
同样分有缓存与无缓存方式，对无缓存方式：
qint64 QAbstractSocket::writeData(const char *data, qint64 size)
Q_D(QAbstractSocket);
if (d->state == QAbstractSocket::UnconnectedState) {
d->socketError = QAbstractSocket::UnknownSocketError;
setErrorString(tr("Socket is not connected"));
return -1;
if (!d->isBuffered) {
qint64 written = d->socketEngine->write(data, size);
if (written < 0) {
d->socketError = d->socketEngine->error();
setErrorString(d->socketEngine->errorString());
} else if (!d->writeBuffer.isEmpty()) {
d->socketEngine->setWriteNotificationEnabled(true);
if (written >= 0)
emit bytesWritten(written);
return written;
char *ptr = d->writeBuffer.reserve(size);
if (size == 1)
*ptr = *data;
memcpy(ptr, data, size);
qint64 written = size;
if (d->socketEngine && !d->writeBuffer.isEmpty())
d->socketEngine->setWriteNotificationEnabled(true);
return written;
}查看QNativeSocketEngine::write()：
qint64 QNativeSocketEngine::write(const char *data, qint64 size)
Q_D(QNativeSocketEngine);
Q_CHECK_VALID_SOCKETLAYER(QNativeSocketEngine::write(), -1);
Q_CHECK_STATE(QNativeSocketEngine::write(), QAbstractSocket::ConnectedState, -1);
return d->nativeWrite(data, size);
qint64 QNativeSocketEnginePrivate::nativeWrite(const char *data, qint64 len)
Q_Q(QNativeSocketEngine);
qint64 ret = 0;
// don't send more than 49152 per call to WSASendTo to avoid getting a WSAENOBUFS
for (;;) {
qint64 bytesToSend = qMin<qint64>(49152, len - ret);
WSABUF buf;
buf.buf = (char*)data + ret;
buf.len = bytesToSend;
DWORD flags = 0;
DWORD bytesWritten = 0;
int socketRet = ::WSASend(socketDescriptor, &buf, 1, &bytesWritten, flags, 0,0);
ret += qint64(bytesWritten);
if (socketRet != SOCKET_ERROR) {
if (ret == len)
break;
continue;
} else if (WSAGetLastError() == WSAEWOULDBLOCK) {
break;
} else {
int err = WSAGetLastError();
WS_ERROR_DEBUG(err);
switch (err) {
case WSAECONNRESET:
case WSAECONNABORTED:
ret = -1;
setError(QAbstractSocket::NetworkError, WriteErrorString);
q->close();
break;
default:
break;
break;
return ret;
}至此分析完毕。
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。
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。
今天分析QNetworkAccessManager、QNetworkRequest和QNetworkReply组成的高级抽象API序列。在动手之前，把doc中有关QNetworkAccessManager的介绍看了一遍。其使用方法大致是：
1 QNetworkAccessManager * manager = new QNetworkAccessManager(this);
2 QNetworkRequest request;
3 request.setUrl(QUrl("http://www.baidu.com"));
4 QNetworkReply * reply = manager->get(request);
5 connect(reply, SIGNAL(readyRead()), this, SLOT(slotReadyRead()));
关键是后面的三行：设定URL、发送并获取响应、读取数据。
在QT自带的例子中也有QNetworkAccessManager的应用：downloadmanager
单步跟踪就用downloadmanager这个例子。
在动手跟踪之前，总结了几个问题：
1、QNetworkAccessManager是更高级的抽象，那么怎么跟QTcpSocket/QUdpSocket联系起来的呢？
2、如果没有跟QTcpSocket联系起来，那么又是怎么跟WSA序列WinAPI联系起来的呢？
3、整个逻辑过程是怎么的呢？
4、获取的（图片或者网页）数据保存在什么地方？
5、跟HTTP或者FTP有关的Cookie、认证等怎么实现的？
6、HTTP的Session相关功能实现了吗？怎么实现的？
在动手分析前，简单介绍一下HTTP协议。HTTP协议是一种为分布式，合作式，超媒体信息系统。它是一种通用的，无状态（stateless）的协议，除了应用于超文本传输外，它也可以应用于诸如名称服务器和分布对象管理系统之类的系统，这可以通过扩展它的请求方法，错误代码和报头来实现。HTTP的一个特点是数据表现形式是可输入的和可协商性的，这就允许系统能被建立而独立于数据传输。HTTP在1990年WWW全球信息刚刚起步的时候就得到了应用。该规范定义的协议用“HTTP/1.1”表示，是对RFC2608[33]的更新。 HTTP协议是通过定义一序列的动作（协议文本中称为方法），来完成数据的传输通信。HTTP1.1版本中有这些方法：get、post、head、options、put、delete、trace、connect。
get方法用于获取URI资源，是最为常用的一种方法。
post方法用于向指定URI提交内容，服务器端响应其行为，该方法也极为常用。
head方法向URI发送请求，仅仅只需要获得响应的协议头。
put方法用于向URI发送请求，若URI不存在，则要求服务器端根据请求创建资源。当URI存在时，服务器端必须接受请求内容，将其作为URI资源的修改后版本。
delete方法用于删除URI标识的指定资源。
trace方法用于激活服务器端对请求的循环反馈，反馈作为http响应的正文内容被传输回客户端。
connect方法通常被用于使用代理连接。
更详细的内容请查看相关资料。
回到QT系统，manager->get()调用其实就是HTTP/1.1协议中get方法的实现。
1 QNetworkReply *QNetworkAccessManager::get(const QNetworkRequest &request)
3 return d_func()->postProcess(createRequest(QNetworkAccessManager::GetOperation, request));
4 }上面的一行程序中有两个调用：
1 QNetworkAccessManager::createRequest()
2 QNetworkAccessManagerPrivate::postProcess()先来看createRequest()，两个参数：第一个参数表示使用Get方法；第二个参数是目标网址。
QNetworkReply *QNetworkAccessManager::createRequest(QNetworkAccessManager::Operation op,
const QNetworkRequest &req,
QIODevice *outgoingData)
Q_D(QNetworkAccessManager);
bool isLocalFile = req.url().isLocalFile();
QString scheme = req.url().scheme().toLower();
// fast path for GET on file:// URLs
// The QNetworkAccessFileBackend will right now only be used for PUT
if ((op == QNetworkAccessManager::GetOperation || op == QNetworkAccessManager::HeadOperation)
&& (isLocalFile || scheme == QLatin1String("qrc"))) {
return new QNetworkReplyFileImpl(this, req, op);
if ((op == QNetworkAccessManager::GetOperation || op == QNetworkAccessManager::HeadOperation)
&& scheme == QLatin1String("data")) {
return new QNetworkReplyDataImpl(this, req, op);
// A request with QNetworkRequest::AlwaysCache does not need any bearer management
QNetworkRequest::CacheLoadControl mode =
static_cast<QNetworkRequest::CacheLoadControl>(
req.attribute(QNetworkRequest::CacheLoadControlAttribute,
QNetworkRequest::PreferNetwork).toInt());
if (mode == QNetworkRequest::AlwaysCache
&& (op == QNetworkAccessManager::GetOperation
|| op == QNetworkAccessManager::HeadOperation)) {
// FIXME Implement a QNetworkReplyCacheImpl instead, see QTBUG-15106
QNetworkReplyImpl *reply = new QNetworkReplyImpl(this);
QNetworkReplyImplPrivate *priv = reply->d_func();
priv->manager = this;
priv->backend = new QNetworkAccessCacheBackend();
priv->backend->manager = this->d_func();
priv->backend->setParent(reply);
priv->backend->reply = priv;
priv->setup(op, req, outgoingData);
return reply;
#ifndef QT_NO_BEARERMANAGEMENT
// Return a disabled network reply if network access is disabled.
// Except if the scheme is empty or file://.
if (!d->networkAccessible && !isLocalFile) {
return new QDisabledNetworkReply(this, req, op);
if (!d->networkSessionStrongRef && (d->initializeSession || !d->networkConfiguration.isEmpty())) {
QNetworkConfigurationManager manager;
if (!d->networkConfiguration.isEmpty()) {
d->createSession(manager.configurationFromIdentifier(d->networkConfiguration));
} else {
if (manager.capabilities() & QNetworkConfigurationManager::NetworkSessionRequired)
d->createSession(manager.defaultConfiguration());
d->initializeSession = false;
#endif
QNetworkRequest request = req;
if (!request.header(QNetworkRequest::ContentLengthHeader).isValid() &&
outgoingData && !outgoingData->isSequential()) {
// request has no Content-Length
// but the data that is outgoing is random-access
request.setHeader(QNetworkRequest::ContentLengthHeader, outgoingData->size());
if (static_cast<QNetworkRequest::LoadControl>
(request.attribute(QNetworkRequest::CookieLoadControlAttribute,
QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Automatic) {
if (d->cookieJar) {
QList<QNetworkCookie> cookies = d->cookieJar->cookiesForUrl(request.url());
if (!cookies.isEmpty())
request.setHeader(QNetworkRequest::CookieHeader, QVariant::fromValue(cookies));
// first step: create the reply
QUrl url = request.url();
QNetworkReplyImpl *reply = new QNetworkReplyImpl(this);
#ifndef QT_NO_BEARERMANAGEMENT
if (!isLocalFile) {
connect(this, SIGNAL(networkSessionConnected()),
reply, SLOT(_q_networkSessionConnected()));
#endif
QNetworkReplyImplPrivate *priv = reply->d_func();
priv->manager = this;
// second step: fetch cached credentials
// This is not done for the time being, we should use signal emissions to request
// the credentials from cache.
// third step: find a backend
priv->backend = d->findBackend(op, request);
if (priv->backend) {
priv->backend->setParent(reply);
priv->backend->reply = priv;
#ifndef QT_NO_OPENSSL
reply->setSslConfiguration(request.sslConfiguration());
#endif
// fourth step: setup the reply
priv->setup(op, request, outgoingData);
return reply;
}代码比较长，主要做了这些事情：
1、设定HTTP请求的头信息（例如客户端请求内容的长度、Cookie等）
2、生成并初始化Reply对象（实际是QNetworkReplyImpl对象）
3、获取本地缓存的认证信息（如果有的话）
4、设定Reply
5、获取一个backend实体
6、如果支持OPENSSL的话，设定SSL的配置
暂时先放一边后面再对createRequest()做进一步的分析，再来看postProcess()
QNetworkReply *QNetworkAccessManagerPrivate::postProcess(QNetworkReply *reply)
Q_Q(QNetworkAccessManager);
QNetworkReplyPrivate::setManager(reply, q);
q->connect(reply, SIGNAL(finished()), SLOT(_q_replyFinished()));
#ifndef QT_NO_OPENSSL
/* In case we're compiled without SSL support, we don't have this signal and we need to
* avoid getting a connection error. */
q->connect(reply, SIGNAL(sslErrors(QList<QSslError>)), SLOT(_q_replySslErrors(QList<QSslError>)));
#endif
#ifndef QT_NO_BEARERMANAGEMENT
activeReplyCount++;
#endif
return reply;
}简单来说就做了一件事情，把QNetworkReply的信号（finished、sslErrors）与QNetworkAccessManager的槽连接起来
接上面，进一步分析QNetworkAccessManager::createRequest()的实现。去除不重要的分支末节，看其调用的QNetworkReplyImplPrivate::setup()和QNetworkAccessManagerPrivate::findBackend()的代码
void QNetworkReplyImplPrivate::setup(QNetworkAccessManager::Operation op, const QNetworkRequest &req,
QIODevice *data)
Q_Q(QNetworkReplyImpl);
outgoingData = data; //outgoingData实际就是QNetworkRequest对象
request = req;
url = request.url();
operation = op;
q->QIODevice::open(QIODevice::ReadOnly);
// Internal code that does a HTTP reply for the synchronous Ajax
// in QtWebKit.
QVariant synchronousHttpAttribute = req.attribute(
static_cast<QNetworkRequest::Attribute>(QNetworkRequest::SynchronousRequestAttribute));
// The synchronous HTTP is a corner case, we will put all upload data in one big QByteArray in the outgoingDataBuffer.
// Yes, this is not the most efficient thing to do, but on the other hand synchronous XHR needs to die anyway.
if (synchronousHttpAttribute.toBool() && outgoingData) {
outgoingDataBuffer = QSharedPointer<QRingBuffer>(new QRingBuffer());
qint64 previousDataSize = 0;
previousDataSize = outgoingDataBuffer->size();
outgoingDataBuffer->append(outgoingData->readAll());
} while (outgoingDataBuffer->size() != previousDataSize);
if (backend)
backend->setSynchronous(synchronousHttpAttribute.toBool());
if (outgoingData && backend && !backend->isSynchronous()) {
// there is data to be uploaded, e.g. HTTP POST.
if (!backend->needsResetableUploadData() || !outgoingData->isSequential()) {
// backend does not need upload buffering or
// fixed size non-sequential
// just start the operation
QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection);
} else {
bool bufferingDisallowed =
req.attribute(QNetworkRequest::DoNotBufferUploadDataAttribute,
false).toBool();
if (bufferingDisallowed) {
// if a valid content-length header for the request was supplied, we can disable buffering
// if not, we will buffer anyway
if (req.header(QNetworkRequest::ContentLengthHeader).isValid()) {
QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection);
} else {
state = Buffering;
QMetaObject::invokeMethod(q, "_q_bufferOutgoingData", Qt::QueuedConnection);
} else {
// _q_startOperation will be called when the buffering has finished.
state = Buffering;
QMetaObject::invokeMethod(q, "_q_bufferOutgoingData", Qt::QueuedConnection);
} else {
// for HTTP, we want to send out the request as fast as possible to the network, without
// invoking methods in a QueuedConnection
#ifndef QT_NO_HTTP
if (qobject_cast<QNetworkAccessHttpBackend *>(backend) || (backend && backend->isSynchronous())) {
_q_startOperation();
} else {
QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection);
#else
if (backend && backend->isSynchronous())
_q_startOperation();
QMetaObject::invokeMethod(q, "_q_startOperation", Qt::QueuedConnection);
#endif // QT_NO_HTTP
}发现调用_q_startOperation函数和_q_bufferOutgoingData函数，代码如下：
void QNetworkReplyImplPrivate::_q_startOperation()
// ensure this function is only being called once
if (state == Working || state == Finished) {
qDebug("QNetworkReplyImpl::_q_startOperation was called more than once");
return;
state = Working;
// note: if that method is called directly, it cannot happen that the backend is 0,
// because we just checked via a qobject_cast that we got a http backend (see
// QNetworkReplyImplPrivate::setup())
if (!backend) {
error(QNetworkReplyImpl::ProtocolUnknownError,
QCoreApplication::translate("QNetworkReply", "Protocol \"%1\" is unknown").arg(url.scheme())); // not really true!;
finished();
return;
if (!backend->start()) {
#ifndef QT_NO_BEARERMANAGEMENT
// backend failed to start because the session state is not Connected.
// QNetworkAccessManager will call _q_startOperation again for us when the session
// state changes.
state = WaitingForSession;
QSharedPointer<QNetworkSession> session(manager->d_func()->getNetworkSession());
if (session) {
Q_Q(QNetworkReplyImpl);
QObject::connect(session.data(), SIGNAL(error(QNetworkSession::SessionError)),
q, SLOT(_q_networkSessionFailed()), Qt::QueuedConnection);
if (!session->isOpen())
session->open();
} else {
qWarning("Backend is waiting for QNetworkSession to connect, but there is none!");
state = Working;
error(QNetworkReplyImpl::UnknownNetworkError,
QCoreApplication::translate("QNetworkReply", "Network session error."));
finished();
#else
qWarning("Backend start failed");
state = Working;
error(QNetworkReplyImpl::UnknownNetworkError,
QCoreApplication::translate("QNetworkReply", "backend start error."));
finished();
#endif
return;
if (backend && backend->isSynchronous()) {
state = Finished;
q_func()->setFinished(true);
} else {
if (state != Finished) {
if (operation == QNetworkAccessManager::GetOperation)
pendingNotifications.append(NotifyDownstreamReadyWrite);
handleNotifications();
}
void QNetworkReplyImplPrivate::_q_bufferOutgoingData()
Q_Q(QNetworkReplyImpl);
if (!outgoingDataBuffer) {
// first call, create our buffer
outgoingDataBuffer = QSharedPointer<QRingBuffer>(new QRingBuffer());
QObject::connect(outgoingData, SIGNAL(readyRead()), q, SLOT(_q_bufferOutgoingData()));
QObject::connect(outgoingData, SIGNAL(readChannelFinished()), q, SLOT(_q_bufferOutgoingDataFinished()));
qint64 bytesBuffered = 0;
qint64 bytesToBuffer = 0;
// read data into our buffer
forever {
bytesToBuffer = outgoingData->bytesAvailable();
// unknown? just try 2 kB, this also ensures we always try to read the EOF
if (bytesToBuffer <= 0)
bytesToBuffer = 2*1024;
char *dst = outgoingDataBuffer->reserve(bytesToBuffer);
bytesBuffered = outgoingData->read(dst, bytesToBuffer);
if (bytesBuffered == -1) {
// EOF has been reached.
outgoingDataBuffer->chop(bytesToBuffer);
_q_bufferOutgoingDataFinished();
break;
} else if (bytesBuffered == 0) {
// nothing read right now, just wait until we get called again
outgoingDataBuffer->chop(bytesToBuffer);
break;
} else {
// don't break, try to read() again
outgoingDataBuffer->chop(bytesToBuffer - bytesBuffered);
}连接两个信号与槽之后，是打开QIODevice，暂未深入分析。然后是呼叫q->_q_startOperation()，实际就是调用QNetworkReplyImpl::_q_startOperation()，使用的是队列等待方式（也就是发送一个消息进入系统消息队列，这个setup函数以及全部后续执行完毕，主动权交回给Windows后，再根据进入队列的消息来触发）。
_q_startOperation就是做了一些简单的判断，然后调用 handleNotifications：
void QNetworkReplyImplPrivate::handleNotifications()
if (notificationHandlingPaused)
return;
NotificationQueue current = pendingNotifications;
pendingNotifications.clear();
if (state != Working)
return;
while (state == Working && !current.isEmpty()) {
InternalNotifications notification = current.dequeue();
switch (notification) {
case NotifyDownstreamReadyWrite:
if (copyDevice)
_q_copyReadyRead();
backend->downstreamReadyWrite();
break;
case NotifyCloseDownstreamChannel:
backend->closeDownstreamChannel();
break;
case NotifyCopyFinished: {
QIODevice *dev = copyDevice;
copyDevice = 0;
backend->copyFinished(dev);
break;
}该函数主要用于处理各种socket相关事件
因此我们先看QNetworkAccessManagerPrivate::findBackend()的代码实现：
QNetworkAccessBackend *QNetworkAccessManagerPrivate::findBackend(QNetworkAccessManager::Operation op,
const QNetworkRequest &request)
if (QNetworkAccessBackendFactoryData::valid) {
QMutexLocker locker(&factoryData()->mutex);
QNetworkAccessBackendFactoryData::ConstIterator it = factoryData()->constBegin(),
end = factoryData()->constEnd();
while (it != end) {
QNetworkAccessBackend *backend = (*it)->create(op, request);
if (backend) {
backend->manager = this;
return backend; // found a factory that handled our request
++it;
return 0;
}这段代码有一点复杂，先看红色标记的第一句，factoryData()是用宏来定义的函数：
Q_GLOBAL_STATIC(QNetworkAccessBackendFactoryData, factoryData)宏定义如下：
#define Q_GLOBAL_STATIC(TYPE, NAME) \
static TYPE *NAME() \
{ \
static TYPE thisVariable; \
static QGlobalStatic<TYPE > thisGlobalStatic(&thisVariable); \
return thisGlobalStatic.pointer; \
}如果对STD比较熟悉，第一感觉这是一个模板List操作。在这里constBegin()和constEnd()组合起来是一个遍历，那么在什么地方设定值呢？良好代码的命名是很规范的，我试了试全局查找factoryData()，找到了我所希望看到的东西：
QNetworkAccessBackendFactory::QNetworkAccessBackendFactory()
QMutexLocker locker(&factoryData()->mutex);
factoryData()->append(this);
QNetworkAccessBackendFactory::~QNetworkAccessBackendFactory()
if (QNetworkAccessBackendFactoryData::valid) {
QMutexLocker locker(&factoryData()->mutex);
factoryData()->removeAll(this);
}里prepend()应该是把对象添加到列表；而removeAll()就是清空全部数据了。
factoryData() 里面包含的对象序列，应该是从QNetworkAccessBackendFactory衍生出来的。
一共有哪些子类呢？继续全局查找
1 class QNetworkAccessDataBackendFactory: public QNetworkAccessBackendFactory
2 class QNetworkAccessDebugPipeBackendFactory: public QNetworkAccessBackendFactory
3 class QNetworkAccessFileBackendFactory: public QNetworkAccessBackendFactory
4 class QNetworkAccessFtpBackendFactory: public QNetworkAccessBackendFactory
5 class QNetworkAccessHttpBackendFactory : public QNetworkAccessBackendFactory去除暂时不关心的DebugPipe，一共有四种：DataBackend、FileBackend、FtpBackend、HttpBackend。媒体的种类原来是在这里实现的。看其中QNetworkAccessHttpBackendFactory::create()。
QNetworkAccessBackend *
QNetworkAccessHttpBackendFactory::create(QNetworkAccessManager::Operation op,
const QNetworkRequest &request) const
// check the operation
switch (op) {
case QNetworkAccessManager::GetOperation:
case QNetworkAccessManager::PostOperation:
case QNetworkAccessManager::HeadOperation:
case QNetworkAccessManager::PutOperation:
case QNetworkAccessManager::DeleteOperation:
case QNetworkAccessManager::CustomOperation:
break;
default:
// no, we can't handle this request
return 0;
QUrl url = request.url();
QString scheme = url.scheme().toLower();
if (scheme == QLatin1String("http") || scheme == QLatin1String("https"))
return new QNetworkAccessHttpBackend;
return 0;
}
如果是能够处理的OP标记并且URL的前缀是http或者是https，则创建一个QNetworkAccessHttpBackend对象。
前面QNetworkAccessManager::get()代码中，调用的参数是QNetworkAccessManager::GetOperation，所以在我们分析的这个应用中，创建的是QNetworkAccessHttpBackend对象。
findBackend()到此分析完毕；由于factoryData()的具体实现跟我们分析网络通信的目标没有太大关系，未深入分析，有谁分析了的话请转告一声，值得一看。
回到前面暂停的QNetworkReplyImpl::_q_startOperation()，又实现了什么动作呢？
首先调用了刚刚创建的QNetworkAccessHttpBackend::start()，然后是添加通知消息、调用_q_sourceReadyRead()、最后处理通知消息：
bool QNetworkAccessBackend::start()
#ifndef QT_NO_BEARERMANAGEMENT
// For bearer, check if session start is required
QSharedPointer<QNetworkSession> networkSession(manager->getNetworkSession());
if (networkSession) {
// session required
if (networkSession->isOpen() &&
networkSession->state() == QNetworkSession::Connected) {
// Session is already open and ready to use.
// copy network session down to the backend
setProperty("_q_networksession", QVariant::fromValue(networkSession));
} else {
// Session not ready, but can skip for loopback connections
// This is not ideal.
const QString host = reply->url.host();
if (host == QLatin1String("localhost") ||
QHostAddress(host) == QHostAddress::LocalHost ||
QHostAddress(host) == QHostAddress::LocalHostIPv6) {
// Don't need an open session for localhost access.
} else {
// need to wait for session to be opened
return false;
#endif
#ifndef QT_NO_NETWORKPROXY
#ifndef QT_NO_BEARERMANAGEMENT
// Get the proxy settings from the network session (in the case of service networks,
// the proxy settings change depending which AP was activated)
QNetworkSession *session = networkSession.data();
QNetworkConfiguration config;
if (session) {
QNetworkConfigurationManager configManager;
// The active configuration tells us what IAP is in use
QVariant v = session->sessionProperty(QLatin1String("ActiveConfiguration"));
if (v.isValid())
config = configManager.configurationFromIdentifier(qvariant_cast<QString>(v));
// Fallback to using the configuration if no active configuration
if (!config.isValid())
config = session->configuration();
// or unspecified configuration if that is no good either
if (!config.isValid())
config = QNetworkConfiguration();
reply->proxyList = manager->queryProxy(QNetworkProxyQuery(config, url()));
#else // QT_NO_BEARERMANAGEMENT
// Without bearer management, the proxy depends only on the url
reply->proxyList = manager->queryProxy(QNetworkProxyQuery(url()));
#endif
#endif
// now start the request
open();
return true;
}start函数很简单，主要是打开QNetworkAccessBackend
话说昨日走到QNetworkReplyImplPrivate::_q_startOperation()，勾引出QNetworkAccessHttpBackend::open()，今日接着欣赏QT之美丽。
1 void QNetworkAccessHttpBackend::open()
3 postRequest();
4 }open函数仅仅是调用postRequest()
etworkAccessHttpBackend::postRequest()
QThread *thread = 0;
if (isSynchronous()) {
// A synchronous HTTP request uses its own thread
thread = new QThread();
QObject::connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
thread->start();
} else if (!manager->httpThread) {
// We use the manager-global thread.
// At some point we could switch to having multiple threads if it makes sense.
manager->httpThread = new QThread();
QObject::connect(manager->httpThread, SIGNAL(finished()), manager->httpThread, SLOT(deleteLater()));
manager->httpThread->start();
#ifndef QT_NO_NETWORKPROXY
qRegisterMetaType<QNetworkProxy>("QNetworkProxy");
#endif
#ifndef QT_NO_OPENSSL
qRegisterMetaType<QList<QSslError> >("QList<QSslError>");
qRegisterMetaType<QSslConfiguration>("QSslConfiguration");
#endif
qRegisterMetaType<QList<QPair<QByteArray,QByteArray> > >("QList<QPair<QByteArray,QByteArray> >");
qRegisterMetaType<QHttpNetworkRequest>("QHttpNetworkRequest");
qRegisterMetaType<QNetworkReply::NetworkError>("QNetworkReply::NetworkError");
qRegisterMetaType<QSharedPointer<char> >("QSharedPointer<char>");
thread = manager->httpThread;
} else {
// Asynchronous request, thread already exists
thread = manager->httpThread;
QUrl url = request().url();
httpRequest.setUrl(url);
bool ssl = url.scheme().toLower() == QLatin1String("https");
setAttribute(QNetworkRequest::ConnectionEncryptedAttribute, ssl);
httpRequest.setSsl(ssl);
#ifndef QT_NO_NETWORKPROXY
QNetworkProxy transparentProxy, cacheProxy;
foreach (const QNetworkProxy &p, proxyList()) {
// use the first proxy that works
// for non-encrypted connections, any transparent or HTTP proxy
// for encrypted, only transparent proxies
if (!ssl
&& (p.capabilities() & QNetworkProxy::CachingCapability)
&& (p.type() == QNetworkProxy::HttpProxy ||
p.type() == QNetworkProxy::HttpCachingProxy)) {
cacheProxy = p;
transparentProxy = QNetworkProxy::NoProxy;
break;
if (p.isTransparentProxy()) {
transparentProxy = p;
cacheProxy = QNetworkProxy::NoProxy;
break;
// check if at least one of the proxies
if (transparentProxy.type() == QNetworkProxy::DefaultProxy &&
cacheProxy.type() == QNetworkProxy::DefaultProxy) {
// unsuitable proxies
QMetaObject::invokeMethod(this, "error", isSynchronous() ? Qt::DirectConnection : Qt::QueuedConnection,
Q_ARG(QNetworkReply::NetworkError, QNetworkReply::ProxyNotFoundError),
Q_ARG(QString, tr("No suitable proxy found")));
QMetaObject::invokeMethod(this, "finished", isSynchronous() ? Qt::DirectConnection : Qt::QueuedConnection);
return;
#endif
bool loadedFromCache = false;
httpRequest.setPriority(convert(request().priority()));
switch (operation()) {
case QNetworkAccessManager::GetOperation:
httpRequest.setOperation(QHttpNetworkRequest::Get);
loadedFromCache = loadFromCacheIfAllowed(httpRequest);
break;
case QNetworkAccessManager::HeadOperation:
httpRequest.setOperation(QHttpNetworkRequest::Head);
loadedFromCache = loadFromCacheIfAllowed(httpRequest);
break;
case QNetworkAccessManager::PostOperation:
invalidateCache();
httpRequest.setOperation(QHttpNetworkRequest::Post);
createUploadByteDevice();
break;
case QNetworkAccessManager::PutOperation:
invalidateCache();
httpRequest.setOperation(QHttpNetworkRequest::Put);
createUploadByteDevice();
break;
case QNetworkAccessManager::DeleteOperation:
invalidateCache();
httpRequest.setOperation(QHttpNetworkRequest::Delete);
break;
case QNetworkAccessManager::CustomOperation:
invalidateCache(); // for safety reasons, we don't know what the operation does
httpRequest.setOperation(QHttpNetworkRequest::Custom);
createUploadByteDevice();
httpRequest.setCustomVerb(request().attribute(
QNetworkRequest::CustomVerbAttribute).toByteArray());
break;
default:
break; // can't happen
if (loadedFromCache) {
// commented this out since it will be called later anyway
// by copyFinished()
//QNetworkAccessBackend::finished();
return; // no need to send the request! :)
QList<QByteArray> headers = request().rawHeaderList();
if (resumeOffset != 0) {
if (headers.contains("Range")) {
// Need to adjust resume offset for user specified range
headers.removeOne("Range");
// We've already verified that requestRange starts with "bytes=", see canResume.
QByteArray requestRange = request().rawHeader("Range").mid(6);
int index = requestRange.indexOf('-');
quint64 requestStartOffset = requestRange.left(index).toULongLong();
quint64 requestEndOffset = requestRange.mid(index + 1).toULongLong();
requestRange = "bytes=" + QByteArray::number(resumeOffset + requestStartOffset) +
'-' + QByteArray::number(requestEndOffset);
httpRequest.setHeaderField("Range", requestRange);
} else {
httpRequest.setHeaderField("Range", "bytes=" + QByteArray::number(resumeOffset) + '-');
foreach (const QByteArray &header, headers)
httpRequest.setHeaderField(header, request().rawHeader(header));
if (request().attribute(QNetworkRequest::HttpPipeliningAllowedAttribute).toBool() == true)
httpRequest.setPipeliningAllowed(true);
if (static_cast<QNetworkRequest::LoadControl>
(request().attribute(QNetworkRequest::AuthenticationReuseAttribute,
QNetworkRequest::Automatic).toInt()) == QNetworkRequest::Manual)
httpRequest.setWithCredentials(false);
// Create the HTTP thread delegate
QHttpThreadDelegate *delegate = new QHttpThreadDelegate;
#ifndef QT_NO_BEARERMANAGEMENT
QVariant v(property("_q_networksession"));
if (v.isValid())
delegate->networkSession = qvariant_cast<QSharedPointer<QNetworkSession> >(v);
#endif
// For the synchronous HTTP, this is the normal way the delegate gets deleted
// For the asynchronous HTTP this is a safety measure, the delegate deletes itself when HTTP is finished
connect(thread, SIGNAL(finished()), delegate, SLOT(deleteLater()));
// Set the properties it needs
delegate->httpRequest = httpRequest;
#ifndef QT_NO_NETWORKPROXY
delegate->cacheProxy = cacheProxy;
delegate->transparentProxy = transparentProxy;
#endif
delegate->ssl = ssl;
#ifndef QT_NO_OPENSSL
if (ssl)
delegate->incomingSslConfiguration = request().sslConfiguration();
#endif
// Do we use synchronous HTTP?
delegate->synchronous = isSynchronous();
// The authentication manager is used to avoid the BlockingQueuedConnection communication
// from HTTP thread to user thread in some cases.
delegate->authenticationManager = manager->authenticationManager;
if (!isSynchronous()) {
// Tell our zerocopy policy to the delegate
delegate->downloadBufferMaximumSize =
request().attribute(QNetworkRequest::MaximumDownloadBufferSizeAttribute).toLongLong();
// These atomic integers are used for signal compression
delegate->pendingDownloadData = pendingDownloadDataEmissions;
delegate->pendingDownloadProgress = pendingDownloadProgressEmissions;
// Connect the signals of the delegate to us
connect(delegate, SIGNAL(downloadData(QByteArray)),
this, SLOT(replyDownloadData(QByteArray)),
Qt::QueuedConnection);
connect(delegate, SIGNAL(downloadFinished()),
this, SLOT(replyFinished()),
Qt::QueuedConnection);
connect(delegate, SIGNAL(downloadMetaData(QList<QPair<QByteArray,QByteArray> >,int,QString,bool,QSharedPointer<char>,qint64)),
this, SLOT(replyDownloadMetaData(QList<QPair<QByteArray,QByteArray> >,int,QString,bool,QSharedPointer<char>,qint64)),
Qt::QueuedConnection);
connect(delegate, SIGNAL(downloadProgress(qint64,qint64)),
this, SLOT(replyDownloadProgressSlot(qint64,qint64)),
Qt::QueuedConnection);
connect(delegate, SIGNAL(error(QNetworkReply::NetworkError,QString)),
this, SLOT(httpError(QNetworkReply::NetworkError, const QString)),
Qt::QueuedConnection);
#ifndef QT_NO_OPENSSL
connect(delegate, SIGNAL(sslConfigurationChanged(QSslConfiguration)),
this, SLOT(replySslConfigurationChanged(QSslConfiguration)),
Qt::QueuedConnection);
#endif
// Those need to report back, therefire BlockingQueuedConnection
connect(delegate, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)),
this, SLOT(httpAuthenticationRequired(QHttpNetworkRequest,QAuthenticator*)),
Qt::BlockingQueuedConnection);
#ifndef QT_NO_NETWORKPROXY
connect (delegate, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),
this, SLOT(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),
Qt::BlockingQueuedConnection);
#endif
#ifndef QT_NO_OPENSSL
connect(delegate, SIGNAL(sslErrors(QList<QSslError>,bool*,QList<QSslError>*)),
this, SLOT(replySslErrors(const QList<QSslError> &, bool *, QList<QSslError> *)),
Qt::BlockingQueuedConnection);
#endif
// This signal we will use to start the request.
connect(this, SIGNAL(startHttpRequest()), delegate, SLOT(startRequest()));
connect(this, SIGNAL(abortHttpRequest()), delegate, SLOT(abortRequest()));
// To throttle the connection.
QObject::connect(this, SIGNAL(readBufferSizeChanged(qint64)), delegate, SLOT(readBufferSizeChanged(qint64)));
QObject::connect(this, SIGNAL(readBufferFreed(qint64)), delegate, SLOT(readBufferFreed(qint64)));
if (uploadByteDevice) {
QNonContiguousByteDeviceThreadForwardImpl *forwardUploadDevice =
new QNonContiguousByteDeviceThreadForwardImpl(uploadByteDevice->atEnd(), uploadByteDevice->size());
if (uploadByteDevice->isResetDisabled())
forwardUploadDevice->disableReset();
forwardUploadDevice->setParent(delegate); // needed to make sure it is moved on moveToThread()
delegate->httpRequest.setUploadByteDevice(forwardUploadDevice);
// From main thread to user thread:
QObject::connect(this, SIGNAL(haveUploadData(QByteArray, bool, qint64)),
forwardUploadDevice, SLOT(haveDataSlot(QByteArray, bool, qint64)), Qt::QueuedConnection);
QObject::connect(uploadByteDevice.data(), SIGNAL(readyRead()),
forwardUploadDevice, SIGNAL(readyRead()),
Qt::QueuedConnection);
// From http thread to user thread:
QObject::connect(forwardUploadDevice, SIGNAL(wantData(qint64)),
this, SLOT(wantUploadDataSlot(qint64)));
QObject::connect(forwardUploadDevice, SIGNAL(processedData(qint64)),
this, SLOT(sentUploadDataSlot(qint64)));
connect(forwardUploadDevice, SIGNAL(resetData(bool*)),
this, SLOT(resetUploadDataSlot(bool*)),
Qt::BlockingQueuedConnection); // this is the only one with BlockingQueued!
} else if (isSynchronous()) {
connect(this, SIGNAL(startHttpRequestSynchronously()), delegate, SLOT(startRequestSynchronously()), Qt::BlockingQueuedConnection);
if (uploadByteDevice) {
// For the synchronous HTTP use case the use thread (this one here) is blocked
// so we cannot use the asynchronous upload architecture.
// We therefore won't use the QNonContiguousByteDeviceThreadForwardImpl but directly
// use the uploadByteDevice provided to us by the QNetworkReplyImpl.
// The code that is in QNetworkReplyImplPrivate::setup() makes sure it is safe to use from a thread
// since it only wraps a QRingBuffer
delegate->httpRequest.setUploadByteDevice(uploadByteDevice.data());
// Move the delegate to the http thread
delegate->moveToThread(thread);
// This call automatically moves the uploadDevice too for the asynchronous case.
// Send an signal to the delegate so it starts working in the other thread
if (isSynchronous()) {
emit startHttpRequestSynchronously(); // This one is BlockingQueuedConnection, so it will return when all work is done
if (delegate->incomingErrorCode != QNetworkReply::NoError) {
replyDownloadMetaData
(delegate->incomingHeaders,
delegate->incomingStatusCode,
delegate->incomingReasonPhrase,
delegate->isPipeliningUsed,
QSharedPointer<char>(),
delegate->incomingContentLength);
replyDownloadData(delegate->synchronousDownloadData);
httpError(delegate->incomingErrorCode, delegate->incomingErrorDetail);
} else {
replyDownloadMetaData
(delegate->incomingHeaders,
delegate->incomingStatusCode,
delegate->incomingReasonPhrase,
delegate->isPipeliningUsed,
QSharedPointer<char>(),
delegate->incomingContentLength);
replyDownloadData(delegate->synchronousDownloadData);
// End the thread. It will delete itself from the finished() signal
thread->quit();
thread->wait(5000);
finished();
} else {
emit startHttpRequest(); // Signal to the HTTP thread and go back to user.
}主要是链接槽函数，看槽函数代码startRequest：
void QHttpThreadDelegate::startRequest()
#ifdef QHTTPTHREADDELEGATE_DEBUG
qDebug() << "QHttpThreadDelegate::startRequest() thread=" << QThread::currentThreadId();
#endif
// Check QThreadStorage for the QNetworkAccessCache
// If not there, create this connection cache
if (!connections.hasLocalData()) {
connections.setLocalData(new QNetworkAccessCache());
// check if we have an open connection to this host
QUrl urlCopy = httpRequest.url();
urlCopy.setPort(urlCopy.port(ssl ? 443 : 80));
#ifndef QT_NO_NETWORKPROXY
if (transparentProxy.type() != QNetworkProxy::NoProxy)
cacheKey = makeCacheKey(urlCopy, &transparentProxy);
else if (cacheProxy.type() != QNetworkProxy::NoProxy)
cacheKey = makeCacheKey(urlCopy, &cacheProxy);
#endif
cacheKey = makeCacheKey(urlCopy, 0);
// the http object is actually a QHttpNetworkConnection
httpConnection = static_cast<QNetworkAccessCachedHttpConnection *>(connections.localData()->requestEntryNow(cacheKey));
if (httpConnection == 0) {
// no entry in cache; create an object
// the http object is actually a QHttpNetworkConnection
#ifdef QT_NO_BEARERMANAGEMENT
httpConnection = new QNetworkAccessCachedHttpConnection(urlCopy.host(), urlCopy.port(), ssl);
#else
httpConnection = new QNetworkAccessCachedHttpConnection(urlCopy.host(), urlCopy.port(), ssl, networkSession);
#endif
#ifndef QT_NO_OPENSSL
// Set the QSslConfiguration from this QNetworkRequest.
if (ssl && incomingSslConfiguration != QSslConfiguration::defaultConfiguration()) {
httpConnection->setSslConfiguration(incomingSslConfiguration);
#endif
#ifndef QT_NO_NETWORKPROXY
httpConnection->setTransparentProxy(transparentProxy);
httpConnection->setCacheProxy(cacheProxy);
#endif
// cache the QHttpNetworkConnection corresponding to this cache key
connections.localData()->addEntry(cacheKey, httpConnection);
// Send the request to the connection
httpReply = httpConnection->sendRequest(httpRequest);
httpReply->setParent(this);
// Connect the reply signals that we need to handle and then forward
if (synchronous) {
connect(httpReply,SIGNAL(headerChanged()), this, SLOT(synchronousHeaderChangedSlot()));
connect(httpReply,SIGNAL(finished()), this, SLOT(synchronousFinishedSlot()));
connect(httpReply,SIGNAL(finishedWithError(QNetworkReply::NetworkError, const QString)),
this, SLOT(synchronousFinishedWithErrorSlot(QNetworkReply::NetworkError,QString)));
connect(httpReply, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)),
this, SLOT(synchronousAuthenticationRequiredSlot(QHttpNetworkRequest,QAuthenticator*)));
connect(httpReply, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),
this, SLOT(synchronousProxyAuthenticationRequiredSlot(QNetworkProxy,QAuthenticator*)));
// Don't care about ignored SSL errors for now in the synchronous HTTP case.
} else if (!synchronous) {
connect(httpReply,SIGNAL(headerChanged()), this, SLOT(headerChangedSlot()));
connect(httpReply,SIGNAL(finished()), this, SLOT(finishedSlot()));
connect(httpReply,SIGNAL(finishedWithError(QNetworkReply::NetworkError, const QString)),
this, SLOT(finishedWithErrorSlot(QNetworkReply::NetworkError,QString)));
// some signals are only interesting when normal asynchronous style is used
connect(httpReply,SIGNAL(readyRead()), this, SLOT(readyReadSlot()));
connect(httpReply,SIGNAL(dataReadProgress(int, int)), this, SLOT(dataReadProgressSlot(int,int)));
#ifndef QT_NO_OPENSSL
connect(httpReply,SIGNAL(sslErrors(const QList<QSslError>)), this, SLOT(sslErrorsSlot(QList<QSslError>)));
#endif
// In the asynchronous HTTP case we can just forward those signals
// Connect the reply signals that we can directly forward
connect(httpReply, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)),
this, SIGNAL(authenticationRequired(QHttpNetworkRequest,QAuthenticator*)));
connect(httpReply, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),
this, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)));
connect(httpReply, SIGNAL(cacheCredentials(QHttpNetworkRequest,QAuthenticator*)),
this, SLOT(cacheCredentialsSlot(QHttpNetworkRequest,QAuthenticator*)));
}先查缓冲，没用的话新建连接，然后调用其sendRequest：
1 QHttpNetworkReply* QHttpNetworkConnection::sendRequest(const QHttpNetworkRequest &request)
3 Q_D(QHttpNetworkConnection);
4 return d->queueRequest(request);
5 }sendRequest()调用queueRequest()函数：
QHttpNetworkReply* QHttpNetworkConnectionPrivate::queueRequest(const QHttpNetworkRequest &request)
Q_Q(QHttpNetworkConnection);
// The reply component of the pair is created initially.
QHttpNetworkReply *reply = new QHttpNetworkReply(request.url());
reply->setRequest(request);
reply->d_func()->connection = q;
reply->d_func()->connectionChannel = &channels[0]; // will have the correct one set later
HttpMessagePair pair = qMakePair(request, reply);
switch (request.priority()) {
case QHttpNetworkRequest::HighPriority:
highPriorityQueue.prepend(pair);
break;
case QHttpNetworkRequest::NormalPriority:
case QHttpNetworkRequest::LowPriority:
lowPriorityQueue.prepend(pair);
break;
// this used to be called via invokeMethod and a QueuedConnection
// It is the only place _q_startNextRequest is called directly without going
// through the event loop using a QueuedConnection.
// This is dangerous because of recursion that might occur when emitting
// signals as DirectConnection from this code path. Therefore all signal
// emissions that can come out from this code path need to
// be QueuedConnection.
// We are currently trying to fine-tune this.
_q_startNextRequest();
return reply;
}在这里整个消息处理（或者是初始化动作）完成之后，按消息序列调用_q_startNextRequest
循环多通道处理请求，类似于connect流程：
void QHttpNetworkConnectionPrivate::_q_startNextRequest()
// If the QHttpNetworkConnection is currently paused then bail out immediately
if (state == PausedState)
return;
//resend the necessary ones.
for (int i = 0; i < channelCount; ++i) {
if (channels[i].resendCurrent && (channels[i].state != QHttpNetworkConnectionChannel::ClosingState)) {
channels[i].resendCurrent = false;
channels[i].state = QHttpNetworkConnectionChannel::IdleState;
// if this is not possible, error will be emitted and connection terminated
if (!channels[i].resetUploadData())
continue;
channels[i].sendRequest();
// dequeue new ones
// return fast if there is nothing to do
if (highPriorityQueue.isEmpty() && lowPriorityQueue.isEmpty())
return;
// try to get a free AND connected socket
for (int i = 0; i < channelCount; ++i) {
if (!channels[i].reply && !channels[i].isSocketBusy() && channels[i].socket->state() == QAbstractSocket::ConnectedState) {
if (dequeueRequest(channels[i].socket))
channels[i].sendRequest();
// try to push more into all sockets
// ### FIXME we should move this to the beginning of the function
// as soon as QtWebkit is properly using the pipelining
// (e.g. not for XMLHttpRequest or the first page load)
// ### FIXME we should also divide the requests more even
// on the connected sockets
//tryToFillPipeline(socket);
// return fast if there is nothing to pipeline
if (highPriorityQueue.isEmpty() && lowPriorityQueue.isEmpty())
return;
for (int i = 0; i < channelCount; i++)
if (channels[i].socket->state() == QAbstractSocket::ConnectedState)
fillPipeline(channels[i].socket);
// If there is not already any connected channels we need to connect a new one.
// We do not pair the channel with the request until we know if it is
// connected or not. This is to reuse connected channels before we connect new once.
int queuedRequest = highPriorityQueue.count() + lowPriorityQueue.count();
for (int i = 0; i < channelCount; ++i) {
if (channels[i].socket->state() == QAbstractSocket::ConnectingState)
queuedRequest--;
if ( queuedRequest <=0 )
break;
if (!channels[i].reply && !channels[i].isSocketBusy() && (channels[i].socket->state() == QAbstractSocket::UnconnectedState)) {
channels[i].ensureConnection();
queuedRequest--;
}接着调用看代码：
bool QHttpNetworkConnectionPrivate::dequeueRequest(QAbstractSocket *socket)
Q_ASSERT(socket);
int i = indexOf(socket);
if (!highPriorityQueue.isEmpty()) {
// remove from queue before sendRequest! else we might pipeline the same request again
HttpMessagePair messagePair = highPriorityQueue.takeLast();
if (!messagePair.second->d_func()->requestIsPrepared)
prepareRequest(messagePair);
channels[i].request = messagePair.first;
channels[i].reply = messagePair.second;
return true;
if (!lowPriorityQueue.isEmpty()) {
// remove from queue before sendRequest! else we might pipeline the same request again
HttpMessagePair messagePair = lowPriorityQueue.takeLast();
if (!messagePair.second->d_func()->requestIsPrepared)
prepareRequest(messagePair);
channels[i].request = messagePair.first;
channels[i].reply = messagePair.second;
return true;
return false;
}看看prepareReuest：
void QHttpNetworkConnectionPrivate::prepareRequest(HttpMessagePair &messagePair)
QHttpNetworkRequest &request = messagePair.first;
QHttpNetworkReply *reply = messagePair.second;
// add missing fields for the request
QByteArray value;
// check if Content-Length is provided
QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice();
if (uploadByteDevice) {
if (request.contentLength() != -1 && uploadByteDevice->size() != -1) {
// both values known, take the smaller one.
request.setContentLength(qMin(uploadByteDevice->size(), request.contentLength()));
} else if (request.contentLength() == -1 && uploadByteDevice->size() != -1) {
// content length not supplied by user, but the upload device knows it
request.setContentLength(uploadByteDevice->size());
} else if (request.contentLength() != -1 && uploadByteDevice->size() == -1) {
// everything OK, the user supplied us the contentLength
} else if (request.contentLength() == -1 && uploadByteDevice->size() == -1) {
qFatal("QHttpNetworkConnectionPrivate: Neither content-length nor upload device size were given");
// set the Connection/Proxy-Connection: Keep-Alive headers
#ifndef QT_NO_NETWORKPROXY
if (networkProxy.type() == QNetworkProxy::HttpCachingProxy) {
value = request.headerField("proxy-connection");
if (value.isEmpty())
request.setHeaderField("Proxy-Connection", "Keep-Alive");
} else {
#endif
value = request.headerField("connection");
if (value.isEmpty())
request.setHeaderField("Connection", "Keep-Alive");
#ifndef QT_NO_NETWORKPROXY
#endif
// If the request had a accept-encoding set, we better not mess
// with it. If it was not set, we announce that we understand gzip
// and remember this fact in request.d->autoDecompress so that
// we can later decompress the HTTP reply if it has such an
// encoding.
value = request.headerField("accept-encoding");
if (value.isEmpty()) {
#ifndef QT_NO_COMPRESS
request.setHeaderField("Accept-Encoding", "gzip");
request.d->autoDecompress = true;
#else
// if zlib is not available set this to false always
request.d->autoDecompress = false;
#endif
// some websites mandate an accept-language header and fail
// if it is not sent. This is a problem with the website and
// not with us, but we work around this by setting
// one always.
value = request.headerField("accept-language");
if (value.isEmpty()) {
QString systemLocale = QLocale::system().name().replace(QChar::fromAscii('_'),QChar::fromAscii('-'));
QString acceptLanguage;
if (systemLocale == QLatin1String("C"))
acceptLanguage = QString::fromAscii("en,*");
else if (systemLocale.startsWith(QLatin1String("en-")))
acceptLanguage = QString::fromAscii("%1,*").arg(systemLocale);
acceptLanguage = QString::fromAscii("%1,en,*").arg(systemLocale);
request.setHeaderField("Accept-Language", acceptLanguage.toAscii());
// set the User Agent
value = request.headerField("user-agent");
if (value.isEmpty())
request.setHeaderField("User-Agent", "Mozilla/5.0");
// set the host
value = request.headerField("host");
if (value.isEmpty()) {
QHostAddress add;
QByteArray host;
if(add.setAddress(hostName)) {
if(add.protocol() == QAbstractSocket::IPv6Protocol) {
host = "[" + hostName.toAscii() + "]";//format the ipv6 in the standard way
} else {
host = QUrl::toAce(hostName);
} else {
host = QUrl::toAce(hostName);
int port = request.url().port();
if (port != -1) {
host += ':';
host += QByteArray::number(port);
request.setHeaderField("Host", host);
reply->d_func()->requestIsPrepared = true;
}按优先级次序发送请求。prepareRequest()设定HTTP请求的Header信息；关键是sendRequest()
bool QHttpNetworkConnectionChannel::sendRequest()
if (!reply) {
// heh, how should that happen!
qWarning() << "QHttpNetworkConnectionChannel::sendRequest() called without QHttpNetworkReply";
state = QHttpNetworkConnectionChannel::IdleState;
return false;
switch (state) {
case QHttpNetworkConnectionChannel::IdleState: { // write the header
if (!ensureConnection()) {
// wait for the connection (and encryption) to be done
// sendRequest will be called again from either
// _q_connected or _q_encrypted
return false;
written = 0; // excluding the header
bytesTotal = 0;
QHttpNetworkReplyPrivate *replyPrivate = reply->d_func();
replyPrivate->clear();
replyPrivate->connection = connection;
replyPrivate->connectionChannel = this;
replyPrivate->autoDecompress = request.d->autoDecompress;
replyPrivate->pipeliningUsed = false;
// if the url contains authentication parameters, use the new ones
// both channels will use the new authentication parameters
if (!request.url().userInfo().isEmpty() && request.withCredentials()) {
QUrl url = request.url();
QAuthenticator &auth = authenticator;
if (url.userName() != auth.user()
|| (!url.password().isEmpty() && url.password() != auth.password())) {
auth.setUser(url.userName());
auth.setPassword(url.password());
connection->d_func()->copyCredentials(connection->d_func()->indexOf(socket), &auth, false);
// clear the userinfo, since we use the same request for resending
// userinfo in url can conflict with the one in the authenticator
url.setUserInfo(QString());
request.setUrl(url);
// Will only be false if QtWebKit is performing a cross-origin XMLHttpRequest
// and withCredentials has not been set to true.
if (request.withCredentials())
connection->d_func()->createAuthorization(socket, request);
#ifndef QT_NO_NETWORKPROXY
QByteArray header = QHttpNetworkRequestPrivate::header(request,
(connection->d_func()->networkProxy.type() != QNetworkProxy::NoProxy));
#else
QByteArray header = QHttpNetworkRequestPrivate::header(request, false);
#endif
socket->write(header);
// flushing is dangerous (QSslSocket calls transmit which might read or error)
// socket->flush();
QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice();
if (uploadByteDevice) {
// connect the signals so this function gets called again
QObject::connect(uploadByteDevice, SIGNAL(readyRead()),this, SLOT(_q_uploadDataReadyRead()));
bytesTotal = request.contentLength();
state = QHttpNetworkConnectionChannel::WritingState; // start writing data
sendRequest(); //recurse
} else {
state = QHttpNetworkConnectionChannel::WaitingState; // now wait for response
sendRequest(); //recurse
break;
case QHttpNetworkConnectionChannel::WritingState:
// write the data
QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice();
if (!uploadByteDevice || bytesTotal == written) {
if (uploadByteDevice)
emit reply->dataSendProgress(written, bytesTotal);
state = QHttpNetworkConnectionChannel::WaitingState; // now wait for response
sendRequest(); // recurse
break;
// only feed the QTcpSocket buffer when there is less than 32 kB in it
const qint64 socketBufferFill = 32*1024;
const qint64 socketWriteMaxSize = 16*1024;
#ifndef QT_NO_OPENSSL
QSslSocket *sslSocket = qobject_cast<QSslSocket*>(socket);
// if it is really an ssl socket, check more than just bytesToWrite()
while ((socket->bytesToWrite() + (sslSocket ? sslSocket->encryptedBytesToWrite() : 0))
<= socketBufferFill && bytesTotal != written)
#else
while (socket->bytesToWrite() <= socketBufferFill
&& bytesTotal != written)
#endif
// get pointer to upload data
qint64 currentReadSize = 0;
qint64 desiredReadSize = qMin(socketWriteMaxSize, bytesTotal - written);
const char *readPointer = uploadByteDevice->readPointer(desiredReadSize, currentReadSize);
if (currentReadSize == -1) {
// premature eof happened
connection->d_func()->emitReplyError(socket, reply, QNetworkReply::UnknownNetworkError);
return false;
break;
} else if (readPointer == 0 || currentReadSize == 0) {
// nothing to read currently, break the loop
break;
} else {
qint64 currentWriteSize = socket->write(readPointer, currentReadSize);
if (currentWriteSize == -1 || currentWriteSize != currentReadSize) {
// socket broke down
connection->d_func()->emitReplyError(socket, reply, QNetworkReply::UnknownNetworkError);
return false;
} else {
written += currentWriteSize;
uploadByteDevice->advanceReadPointer(currentWriteSize);
emit reply->dataSendProgress(written, bytesTotal);
if (written == bytesTotal) {
// make sure this function is called once again
state = QHttpNetworkConnectionChannel::WaitingState;
sendRequest();
break;
break;
case QHttpNetworkConnectionChannel::WaitingState:
QNonContiguousByteDevice* uploadByteDevice = request.uploadByteDevice();
if (uploadByteDevice) {
QObject::disconnect(uploadByteDevice, SIGNAL(readyRead()), this, SLOT(_q_uploadDataReadyRead()));
// HTTP pipelining
//connection->d_func()->fillPipeline(socket);
//socket->flush();
// ensure we try to receive a reply in all cases, even if _q_readyRead_ hat not been called
// this is needed if the sends an reply before we have finished sending the request. In that
// case receiveReply had been called before but ignored the server reply
if (socket->bytesAvailable())
QMetaObject::invokeMethod(this, "_q_receiveReply", Qt::QueuedConnection);
break;
case QHttpNetworkConnectionChannel::ReadingState:
// ignore _q_bytesWritten in these states
// fall through
default:
break;
return true;
}进行的底层的socket调用，不详细分析
QHttpNetworkConnection的构造中，有些我们感兴趣的东西：
QHttpNetworkConnection::QHttpNetworkConnection(const QString &hostName, quint16 port, bool encrypt, QObject *parent, QSharedPointer<QNetworkSession> networkSession)
: QObject(*(new QHttpNetworkConnectionPrivate(hostName, port, encrypt)), parent)
Q_D(QHttpNetworkConnection);
d->networkSession = networkSession;
d->init();
}继续跟进 init函数：
void QHttpNetworkConnectionPrivate::init()
for (int i = 0; i < channelCount; i++) {
channels[i].setConnection(this->q_func());
channels[i].ssl = encrypt;
#ifndef QT_NO_BEARERMANAGEMENT
//push session down to channels
channels[i].networkSession = networkSession;
#endif
channels[i].init();
}接下来看channels的init函数：
void QHttpNetworkConnectionChannel::init()
#ifndef QT_NO_OPENSSL
if (connection->d_func()->encrypt)
socket = new QSslSocket;
socket = new QTcpSocket;
#else
socket = new QTcpSocket;
#endif
#ifndef QT_NO_BEARERMANAGEMENT
//push session down to socket
if (networkSession)
socket->setProperty("_q_networksession", QVariant::fromValue(networkSession));
#endif
#ifndef QT_NO_NETWORKPROXY
// Set by QNAM anyway, but let's be safe here
socket->setProxy(QNetworkProxy::NoProxy);
#endif
QObject::connect(socket, SIGNAL(bytesWritten(qint64)),
this, SLOT(_q_bytesWritten(qint64)),
Qt::DirectConnection);
QObject::connect(socket, SIGNAL(connected()),
this, SLOT(_q_connected()),
Qt::DirectConnection);
QObject::connect(socket, SIGNAL(readyRead()),
this, SLOT(_q_readyRead()),
Qt::DirectConnection);
// The disconnected() and error() signals may already come
// while calling connectToHost().
// In case of a cached hostname or an IP this
// will then emit a signal to the user of QNetworkReply
// but cannot be caught because the user did not have a chance yet
// to connect to QNetworkReply's signals.
qRegisterMetaType<QAbstractSocket::SocketError>("QAbstractSocket::SocketError");
QObject::connect(socket, SIGNAL(disconnected()),
this, SLOT(_q_disconnected()),
Qt::QueuedConnection);
QObject::connect(socket, SIGNAL(error(QAbstractSocket::SocketError)),
this, SLOT(_q_error(QAbstractSocket::SocketError)),
Qt::QueuedConnection);
#ifndef QT_NO_NETWORKPROXY
QObject::connect(socket, SIGNAL(proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),
this, SLOT(_q_proxyAuthenticationRequired(QNetworkProxy,QAuthenticator*)),
Qt::DirectConnection);
#endif
#ifndef QT_NO_OPENSSL
QSslSocket *sslSocket = qobject_cast<QSslSocket*>(socket);
if (sslSocket) {
// won't be a sslSocket if encrypt is false
QObject::connect(sslSocket, SIGNAL(encrypted()),
this, SLOT(_q_encrypted()),
Qt::DirectConnection);
QObject::connect(sslSocket, SIGNAL(sslErrors(QList<QSslError>)),
this, SLOT(_q_sslErrors(QList<QSslError>)),
Qt::DirectConnection);