QtWebChannel question

[Anton Kreuzkamp]

Hi,

yes, QtWebChannel is supposed to do client-server-communication. Currently it 
only works with a C++/Qt based server (which I use in a personal project). But 
theoretically (and that's the goal after all) it's possible to do the 
communication between a nodejs/php/JavaEE/... server and a qmlweb client using 
QtWebChannel (that's possible, as soon as someone implements the server side 
of the protocol for those server-technologies).

To use it on client side:

1. include qwebchannel.js into your index.html: 
    <script type="text/javascript" src="qmlweb/src/qwebchannel.js"></script>

2. instanciate a websocket and a webchannel in your js-code:

var socket = new WebSocket('example.com:8080/myWebSocketServer');
var myObj;

socket.onclose = function() {
    console.log("web channel closed.");
};
socket.onerror = function(error) {
    console.error("web channel error: " + error);
};
socket.onopen = function() {
    new QWebChannel(socket, function(channel) {
	// Stuff we do when the remote object arrives.
        myObj = channel.objects.myObj;
        myObj.someSignal.connect(function(someArg) {
		//...
        });
    });
}

3. In Qml do whatever you want with it (you can just access your object using 
myObj). But attention: You always have to handle the case, the object is not 
yet there. Alternatively you can create the QML scene just when the object 
arrived.
I plan to implement QMLEngine.registerSingleton(), though, which would then 
wait for the channel to be ready, synchronously.


4. For the (C++/Qt-) server side you need (e.g. in your main()):

QWebChannel channel;
QWebSocketServer server("QWebChannel Standalone Example Server", 
QWebSocketServer::NonSecureMode);
if (!server.listen(QHostAddress::Any, 10002)) {
    qFatal("Failed to open web socket server.");
    return 1;
}

MyObj myObj;

QObject::connect(&server, &QWebSocketServer::newConnection, [&] () {
    channel.connectTo(new WebSocketTransport(server.nextPendingConnection()));
    // Do some init stuff...
});

channel.registerObject("myObj", &myObj);

Cheers, Anton


On Monday 02 March 2015 21:00:47 you wrote:
> Anton, hi again!! ;-)
> 
> I noted that you made some deeds on QtWebChannel  thing.
> 
> Could you please describe, how could it be used?
> 
> I googled some info and found
> http://www.kdab.com/qt-webchannel-bridging-gap-cqml-web/
> but I cannot understand, if we are already in browser, how
> do you consider to use QtWebChannel?
> 
> Can it be used for browser-server communication?
> 
> e.g. can I load some qml objects in nodejs and communicate
> with browser using QtWebChannel?
> 
> Best Regards,
> Pavel Vasev

-- 
Gruß auch an die NSA.
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