i was going to switch some codebase to websocket server, too, but reading this lets me think again...
thanks ;)
Am Thu, 4 Apr 2019 16:33:19 +0200
schrieb "Jason H" <jh...@gmx.com>:
> I looked at the private implementation of QWebSocketServer,
> QWebSocketServerPrivate.
>
> I haven't tested it, but there are a few concerns:
>
> 1. That for errorString(), it first checks if it doesn't have an error then
> returns the QTcpSocket errorString(). But if you just look at serverError()
> it only reports it's own error and nothing at the QTcpSocket level. This
> means that if you only check serverError() you won't catch QTcpServer error.
> This is probably a bug. QWebSocketProtocol::CloseCode needs to be able to
> express QAbstractSocket::SocketErrors as well.
>
> 2. QWebSocketServerPrivate::handshakeReceived() has a check of
> pTcpSocket->bytesAvailable()).endsWith(QByteArrayLiteral("\r\n\r\n") Such
> position-reliant checks are bad form. There's no reason for it to end with,
> it should probably be using contains()
>
> 3. There are multiple `if` blocks that don't set an error. This isn't wrong,
> as the handhake bytes may come in slowly and take multiple re-parsings,
> (something to add to your fuzzer?) but you can wind up in an uncaught error
> state.
>
>
>
> Sent: Thursday, April 04, 2019 at 10:07 AM
> From: "Jason H" <jh...@gmx.com>
> To: "Narolewski Jakub" <izow...@gmail.com>
> Cc: interest@qt-project.org
> Subject: Re: [Interest] QWebSocketServer - server randomly stops accepting
> connections
> So, yeah, I was thinking of QTcpServer::incommingConnection(). That function
> is used in multithreadding because you use the descriptor to make a socket on
> the proper thread. Looks like QWebSocketServer is not multithreaded.
>
> I've used Qt's websockets, and I've used QTcpServer extensively on 5-nines
> stuff. Never saw anything like this.
>
> Next steps:
> - QWebSocketServer::setMaxPendingConnections() set this to 0, 1, or 100, see
> what (if anything) changes.
> - Use QTcpServer to and QWebSocketServer::handleConnection(QTcpSocket*) to
> handle the connection yourself just to get QWebSocketServer out of the
> initial connection stuff.
>
> Whatever the cause, I think you're in bug territory, either in Qt or the
> linux kernel. Both of those is unlikely. There is one more possibilty, if
> you're using secure sockets, maybe something is failing at the SSL level?
> Like your SSL implementation stops working for whatever reason?
>
> Sent: Thursday, April 04, 2019 at 9:13 AM
> From: "Narolewski Jakub" <izow...@gmail.com>
> To: "Jason H" <jh...@gmx.com>
> Cc: interest@qt-project.org
> Subject: Re: [Interest] QWebSocketServer - server randomly stops accepting
> connections
> That's the thing. I already handle connections and disconnections in my code
> - including logging relevant information.
> When I implemented this I heavily based on the example that you linked to.
> WSS communication is single threaded - only way to communicate with the
> outside world from different thread is to send custom QEvent onto the Server
> instance.
> QWebSocketServer does not seem to have the method incomingConnection in it's
> public API or maybe I already went mad :P I react to the
> QWebSocketServer::newConnection signal.
>
> Last RST from client at 33 second mark is our client-side timeout.
> This is the code that handles websocket stuff, I have stripped some parts
> that are less important:
>
> // server connects
> connect(m_wsServer, &QWebSocketServer::acceptError, this,
> [this](QAbstractSocket::SocketError socketError) {
> qCritical() << "QWebSocketServer - acceptError:" << socketError;
> });
>
> connect(m_wsServer, &QWebSocketServer::peerVerifyError, this, [this](const
> QSslError& error) {
> qCritical() << "QWebSocketServer - peerVerifyError:" << error;
> });
>
> connect(m_wsServer, &QWebSocketServer::serverError, this,
> [this](QWebSocketProtocol::CloseCode closeCode) {
> qCritical() << "QWebSocketServer - serverError:" << closeCode;
> });
>
> connect(m_wsServer, &QWebSocketServer::sslErrors, this, [this](const
> QList<QSslError>& errors) {
> qCritical() << "QWebSocketServer - sslErrors:" << errors;
> });
>
> connect(m_wsServer, &QWebSocketServer::closed, this, [this]() {
> qCritical() << "QWebSocketServer - closed, serverError():" <<
> m_wsServer->errorString();
> });
>
> connect(m_wsServer, &QWebSocketServer::newConnection, this, [this]() {
> QWebSocket* clientSocket = m_wsServer->nextPendingConnection();
> qInfo() << "Got connection from client:" <<
> clientSocket->peerAddress();
>
> [ client initialization stuff ]
>
> connect(clientSocket, &QWebSocket::binaryMessageReceived, this,
> [this](const QByteArray& message) {
> auto client = sender()->property("client").value<Client*>();
>
> [ message deserialization ]
> });
>
> connect(clientSocket, &QWebSocket::disconnected, this, [this]() {
> auto client = sender()->property("client").value<Client*>();
> qInfo() << client->sayHello() << "is disconnected.";
>
> client->handleDisconnection();
>
> [ clinet cleanup stuff ]
> });
> });
>
> Client's handleDisconnection() function does:
>
> void i9ms::Client::handleDisconnection()
> {
> m_isConnected = false;
> m_websocket->deleteLater();
> m_websocket = nullptr;
> }
>
> Nothing from this lands in system logs. It seems that
> QWebSocketServer::newConnection() is just not emited.
> As I wrote earlier I have a timerEvent that logs QWebSocketServer's state -
> once every ten minutes.
> It happily reports that server is listening, has no pending connections and
> it's internal 'errorString' is empty - even if it is mute from the outside.
>
> It's hard for me to pinpoint exactly what causes this. 'Time' is my best
> guess.
> I'm also not sure if quantity of connections plays a role here.
>
> I have a 'fuzzer-bot' that spams hundreds of connections and messages at the
> server in short period of time.
> Malformed messages, out-of-order client state changes, ugly words - you name
> it we have it.
> QWebSocketServer handles it well enough for us but then, at some time in
> future WHILE being completely idle, server goes silent.
> On the other hand I can start the server, connect - disconnect one client,
> leave it for a while in idle and same thing happens, leaving me one step
> closer to dementia.
>
> On Wed, 3 Apr 2019, 22:32 Jason H, <jh...@gmx.com> wrote:
> Addendum,
> >
> > How much does you code diverge from the example?
> > https://doc.qt.io/qt-5/echoserver.html
> > Can you hack that to receive your traffic or augment your code to to do
> > what it does?
> > Note that the QWebSocket server does not take ownership of the QWebSocket,
> > you have to track that manually. Using the code they provide, I would also
> > log your connected clients. See the slot EchoServer::socketDisconnected()
> > _______________________________________________ Interest mailing list
> > Interest@qt-project.org https://lists.qt-project.org/listinfo/interest
>
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*/
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