Sending an HTTP request using QNetworkAccessManager

问题

I've got a problem trying to send a request using QNetworkAccessManager from a QObject derived class.

Firstly in my constructor I do the following:

QObject::connect( &mAccessManager, SIGNAL( finished( QNetworkReply* ) ), this, SLOT( requestFinished( QNetworkReply* ) ) );

Then when I wish to send the request I do the following:

QNetworkRequest checkLogin( QUrl( address ) );
checkLogin.setHeader( QNetworkRequest::ContentTypeHeader, "application/x-www-form-urlencoded" );

mByteArray  = QByteArray( "POST \"client\" : oxres" );
QNetworkReply* pReply   = mAccessManager.post( checkLogin, mByteArray );

Now at this point I expect to wait around for a few seconds and then receive a response to my class's slot requestFinished. It doesn't however get called.

I'm at a loss as to what I'm doing wrong. Anyone got any ideas? (I'm sure its something stupidly simple).

Edit: Ok this is very weird. I have wireshark collecting packets in the background and when i generate that post request I see nothing happening in wireshark. So why isn't it sending??

Edit 2: Hmm it seems that the problem lies with me sending a request to an https:// address ... why would that be??

回答1:

A few points:

1) The thread your QNetworkRequest belongs to must be running event loop (only this way you can receive signals).

2) If you "wait around" with something like sleep after mAccessManager.post it is not going to work. You have to let event loop iterate to process signals, etc. You can run event loop yourself after post.

ADD:

I did it synchronously like this

QNetworkRequest request;

request.setHeader(
            QNetworkRequest::ContentTypeHeader,
            QVariant( QString("text/xml") )
            );
request.setHeader(
            QNetworkRequest::ContentLengthHeader,
            QVariant( qulonglong(mesPOST.size()) )
            );
request.setHeader(...);
//etc....

request.setAttribute(
            QNetworkRequest::CacheLoadControlAttribute,
            QVariant( int(QNetworkRequest::AlwaysNetwork) )
            );
request.setUrl( QUrl( "http://bla.bla", QUrl::StrictMode ) );

QNetworkReply* pReply = m_NetMgr->post( request, mesPOST );
QEventLoop eLoop;

QObject::connect( pReply, SIGNAL(finished()), &eLoop, SLOT(quit()) );
eLoop.exec( QEventLoop::ExcludeUserInputEvents );

回答2:

Ok so it turns out the problem is caused byt the fact that Qt does not include SSL support by default.

http://doc.qt.nokia.com/4.7/ssl.html

回答3:

I think this is because QNetworkAccessManager is asynchronous and need the time to send the request. But require, url, query, ... is destroyed when out of scope.
-> we need in scope when QNetworkAccessManager do send request (use QEventLoop().exec(); ) or let require, url, query, ... is persistent (declare it with static). See: Qt: QNetworkAccessManager dont send request

来源：https://stackoverflow.com/questions/6204621/sending-an-http-request-using-qnetworkaccessmanager

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