Extending networking/socket programming functionality of a qml project

qcoderpro

Sorry, there was a problem with my connection. Now that I runt the two apps (on my Windows machine), they both run successfully (with no errors) but messages won't be sent/received. That is, whatever I write and click on the Send button, nothing appears on the other side! :(

When sending messages on the server app, the error below appears on the Application Output window:
"QIODevice::write (QTcpSocket): device not open"

SGaist

You are mixing noip API server and yours. They are not the same and the port you use for your application is unrelated to the one you use to update your account.

As for your socket issue, I do not see any error checking done in your code so you do not even know whether your connection was successful.

qcoderpro

@SGaist

You are mixing noip API server and yours. They are not the same and the port you use for your application is unrelated to the one you use to update your account.

Sounds reasonable. So what port number should I use for my client app to be able to connect to the server app, please? The sever sends its IP by updating the record, but how about a port? How to find a port for the connection?

jsulm

@qcoderpro said in Extending networking/socket programming functionality of a qml project:

So what port number should I use for my client app to be able to connect to the server app, please?

The port your server is listening for connections.
It is your server, so you should know what server you use.

qcoderpro

@jsulm
The server may be run by someone in another country, so how the client should know the port number!? :|
Furthermore, you said: port number can be fixed (like 8080 for HTTP).

For the connection both IP and port are needed, As far as I'm concerned. No-ip works out the problem with IP. But how about the port number? :(

jsulm

@qcoderpro Question: do you have to use a fix port number or not? Port can be fixed like it is for many protocols.

qcoderpro

@jsulm
I don't know since I'm new to networking. Actually I chose Qt to learn socket programming. When running the apps on the same machine, the client needs both IP and port to connect to the server. The server publishes both, say, this for the port: QString::number(tcpServer->serverPort()), and since I can see them, I enter IP and port in client's fields to connect to server.
Now that the apps are going to work remotely, for example, each running by a person in a different location (not on the same machine), the IP problem is going to be fixed using noip. But the port problem remains. So I assume there're two ways to work it out, 1- use a fixed port or 2- use any port the server offers but this way we need to somehow deliver that number to client to give it the ability to establish the connection.
Now you choose what to choose please.

SGaist

That's your application so that decision is yours.

As you were already explained, peer to peer communication has different constraints than the use of a central server.

qcoderpro

@SGaist
Since I've not been dealt with projects like that, I'm seeking the easiest way. An easy free service like No-ip. I wish it could solve the issue with the port as well. :|
What do you suggest, please?

jsulm

@qcoderpro said in Extending networking/socket programming functionality of a qml project:

What do you suggest, please?

I suggest to use a fixed port number...

qcoderpro

@jsulm
Good. Could you also guide me how to do that? I mean if there's any reference or Docs page to help me learn how to do that I will be appreciative.

SGaist

https://en.m.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers

qcoderpro

@SGaist
Sorry for the delay. I was very busy. If you think it's better, I'm going to create a new thread for the problem.

I checked the page for the ports numbers and tested a couple of them which are related to messaging based on TCP.

My server.cpp has:

Server::Server(QObject *parent)
    : QObject{parent}
    , tcpSocket(new QTcpSocket(this))
    , tcpServer(new QTcpServer(this))
{
    initServer();
}

QString Server::initServer() {

    tcpServer = new QTcpServer(this);
    if(!tcpServer->listen())
        return "Server Unable to start the server: " +
                tcpServer->errorString();

    connect(tcpServer, &QTcpServer::newConnection, this, &Server::onNewConnection);

    QByteArray auth = "myEmail@gmail.com:myPass";
    QByteArray authHeaderData = "Basic " + auth.toBase64();

    QUrl requestUrl("https://dynupdate.no-ip.com/nic/update");
    requestUrl.setQuery("hostname=coderdev.ddns.net");

    QNetworkRequest request(requestUrl);
    request.setRawHeader("Authorization", authHeaderData);

    QNetworkAccessManager* qnam = new QNetworkAccessManager(this);
    QNetworkReply * reply = qnam->get(request);

    if(reply->error())
        qInfo() << "ERROR!: " + reply->errorString();
    else
        qInfo() << "Reply got back with no error!";
}

void Server::onNewConnection() {

    qInfo() << "New connection arrived!";

    tcpSocket = tcpServer->nextPendingConnection();
    connect(tcpSocket, &QAbstractSocket::errorOccurred, this, &Server::displayError);
    inOut.setDevice(tcpSocket);
    inOut.setVersion(QDataStream::QDataStream::Qt_5_10);
    connect(tcpSocket, &QAbstractSocket::readyRead, this, &Server::writeMessage);
}
...

First ran this app and got the message: Reply got back with no error!

client.cpp contains:

Client::Client(QObject *parent)
    : QObject{parent}
    , tcpSocket(new QTcpSocket(this))
{
    inOut.setDevice(tcpSocket);
    inOut.setVersion(QDataStream::Qt_5_10);
    connect(tcpSocket, &QAbstractSocket::readyRead, this, &Client::writeMessage);
    connect(tcpSocket, &QAbstractSocket::errorOccurred, this, &Client::displayError);

    QHostInfo info = QHostInfo::fromName("coderdev.ddns.net");
    sendAddress(info.addresses().front(), 4662);

    /*   18	Message Send Protocol[19][20]
         157	Assigned  KNET/VM Command/Message Protocol
         218	Message posting protocol (MPP)
         993	Internet Message Access Protocol over TLS/SSL (IMAPS)[11]
         2123	GTP control messages (GTP-C)
         2152	GTP user data messages (GTP-U)
         2775	Short Message Peer-to-Peer (SMPP)[citation need
         4662	OrbitNet Message Service
    */
}

void Client::sendAddress(QHostAddress ip, unsigned int port)
{
    tcpSocket->abort();
    tcpSocket->connectToHost(ip, port);
}
...

After running the server (and hoping that the record on noip has been updated correctly), ran the client and tested all ports above!
Yet no new connection nor an error from the displayError slot.
But Qt Creator gives the error: Cannot retrieve debugging output. for all of the ports!

Where is the problem, please? :(

SGaist

You do not set the port on the server.

Also, you create the QTcpServer object twice. Not an issue per se but it does not make any sense.

qcoderpro

@SGaist
Yeah thank you.

In the previous version (when the two app run on the same machine) we don't have port setting. How to set the port on the server, please?

SGaist

It's all in the documentation of the listen method.

qcoderpro

I firstly run the server and get: Reply got back with no error!, for this code:

void Server::initServer() {

    if(!tcpServer->listen(QHostAddress::Any, 4662))
        qInfo() << "Server Unable to start the server: " +
                tcpServer->errorString();

    connect(tcpServer, &QTcpServer::newConnection, this, &Server::onNewConnection);

    QByteArray auth = "myEmail@gmail.com:myPass";
    QByteArray authHeaderData = "Basic " + auth.toBase64();

    QUrl requestUrl("https://dynupdate.no-ip.com/nic/update");
    requestUrl.setQuery("hostname=coderdev.ddns.net");

    QNetworkRequest request(requestUrl);
    request.setRawHeader("Authorization", authHeaderData);

    QNetworkAccessManager* qnam = new QNetworkAccessManager(this);
    QNetworkReply * reply = qnam->get(request);

    if(reply->error())
        qInfo() << "ERROR!: " + reply->errorString();
    else
        qInfo() << "Reply got back with no error!";
}

Then when running the client and texting, nothing is shown on the other side and get the error: QIODevice::write (QTcpSocket): device not open, on the server. :|

qcoderpro

My hostname is also active.

SGaist

Do you realize that QNetworkAccessManager is asynchronous ?

qcoderpro

@SGaist

I know that asynchronous tasks can work in parallel but don't know what it has to do with the error I get! :(
What is the problem that the projects can't connect together and work, please?