"Connection closed" When using QNetworkAccessManager and QTcpServer

[Ildar]

I have simple server with QTcpServer and simple client with QNetworkAccessManager.

1. When I request data from the server via curl or browser everything is ok
2. When I request data from any site via QNetworkAccessManager everything is ok
3. But I can not read data from QTcpServer via QNetworkAccessManager. All requests are reseted. QNetworkAccessManager (client) had send RST (reset connection) right after it received a data from server. You could see the Wireshark logs. And in client code we get the error: "Connection closed" (RemoteHostClosedError)
4. Aslo, I tried use QNetworkAccessManager from DownloadManager example and QTcpServer from FortuneServer example in various combinations, but the results were the same.

Tested Qt Versions:

• Mac Qt 5.7
• Linux Qt 5.7
• Linux Qt 5.6.2
• Linux Qt 5.5.1

Wireshark logs:
https://drive.google.com/file/d/0B0Pb09eHyZTfUThQNTctQVJOUVU/view?usp=sharing

Wireshark screenshot: qt-wireshark.png
The upper parts (with red lines) are results of QNetworkAccessManager, and the latest packets with success result are curl attempt to get data from QTcpServer

Also there is a simple example to reproduce the error: testNetwork.zip

And here is sample code for client:

void test(quint16 port)
{
    QNetworkAccessManager *manager = new QNetworkAccessManager();

    QNetworkRequest request;
    request.setUrl(QUrl(QString("http://127.0.0.1:%1/").arg(port)));

    manager->connect(manager, &QNetworkAccessManager::finished,
                     [](QNetworkReply *reply) {
        qDebug() << QString("Finished. %1. %2").arg(reply->errorString()).arg(reply->error());
        qDebug() << "readed: " << reply->readAll();
    });

    QNetworkReply *reply = manager->get(request);

    reply->connect(reply, &QNetworkReply::readyRead, [reply]() {
        qDebug() << QString("readyRead: '%1'").arg(QString(reply->readAll()));
    });
}

and for server:

    QTcpSocket socket;
    ...
    if(socket.waitForReadyRead(5000))
    {
        QByteArray request;
        request += socket.readAll();

        QByteArray responce("HELLO, WORLD! HELLO, WORLD! HELLO, WORLD! HELLO, WORLD!");

        socket.write(responce);
        if(!socket.waitForBytesWritten())
        {
            qWarning() << QString("Error occurred in waitForBytesWritten() method of the tcp socket. %1 (%2)")
                          .arg(socket.errorString())
                          .arg(socket.error());
        }
    }
    else
    {
        qWarning() << QString("Error occurred in read method of the tcp socket. %1 (%2)")
                      .arg(socket.errorString())
                      .arg(socket.error());
    }

Also I created a Bug Report

[raven-worx]

@Ildar said in "Connection closed" When using QNetworkAccessManager and QTcpServer:

Also I created a Bug Report

This is not a bug!
Since you are using QNetworkAccessManager you are sending HTTP requests to your server. And QNAM of course expects a HTTP response.

At least the response should look like the following.

Note:

• each line should end with \r\n
• an empty line separates the header- and content-section
• Content-Length header is the byte-count of the content

HTTP/1.1 200 OK
Date: Thu, 20 Oct 2016 12:28:53 GMT
Server: MyServer 1.0.0
Content-Length: 3
Content-Type: text/plain
Connection: Closed

XXX

You are simply sending the content directly. So no status line (HTTP/1.1 200 OK) to indicate the result, thus QNAM closes the connection due to an unexpected response.

[Ildar]

@raven-worx Thank you very much for your response!