Error while using QTcpSocket

Question

I am creating a (very basic) MJPG server to show webcam data on a browser. I have partly managed to do it so far.

Here is my code:

TcpSe         


        

Answer 1

Here Is the Code I used to open the MJPEG Streaming Server in my original Project. Perhaps It can help you finding out your Problem.

void MjpegStreamingEngine::StartServer(){

    m_TcpHttpServer = new QTcpServer();

    m_TcpHttpServer->connect(m_TcpHttpServer,
                             SIGNAL(newConnection()),
                             this,
                             SLOT(TcpHttpconnected()));

    m_TcpHttpServer->listen(QHostAddress::Any,
                            8889);
}

void MjpegStreamingEngine::TcpHttpconnected(){

    m_TcpHttpClient = m_TcpHttpServer->nextPendingConnection();

    m_TcpHttpClient->connect(m_TcpHttpClient,
                             SIGNAL(readyRead()),
                             this,
                             SLOT(TcpHttpreadyRead()));

}

void MjpegStreamingEngine::TcpHttpreadyRead(){

    m_TcpHttpClient->readAll(); // Discard "Get Request String"

    QByteArray ContentType = ("HTTP/1.0 200 OK\r\n" \
                              "Server: en.code-bude.net example server\r\n" \
                              "Cache-Control: no-cache\r\n" \
                              "Cache-Control: private\r\n" \
                              "Content-Type: multipart/x-mixed-replace;boundary=--boundary\r\n\r\n");

    m_TcpHttpClient->write(ContentType);


    while(1){

        if (m_TcpHttpClient->isOpen())
        {

            // Send Image

            QThread::msleep(10);

        }else{
            return;
        }

    }

    m_TcpHttpClient->disconnect(); //Should never be Reached
}

Answer 2

It looked like the socket got closed

Rather than guessing, connect to the error signals of TCPServer and TCPSocket to know when errors occur, or when a client disconnects.

The problem you have is the while(1) loop. Qt is an event-driven framework, so having code in an infinite loop on the main thread is going to prevent events being delivered.

Instead of the infinite loop, connect to QTcpSocket::readyRead signal and handle the data when the connected slot is called.

Qt demonstrates this with the Fortune Server and Fortune Client example code.

If you're using C++ 11, you can use a connection to a lambda function to handle the readyRead, like this

void TcpServer::newConnection()
{
    ...

    QTcpSocket *m_TcpHttpClient = server->nextPendingConnection();
    connect(m_TcpHttpClient, &QTcpSocket::readyRead, [=](){

        // handle received data here

    });

}