Extending networking/socket programming functionality of a qml project

[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?

[qcoderpro]

There're many differences between synchronous and asynchronous data transmission. But despite many disadvantages asynchronous transmission involves it's still possible to use it for my two apps, otherwise you wouldn't suggest QNetworkAccessManager for that, I'm sure.
Do you mean that the data I send from the server to client or vice versa will be corrupted or dropped when traversing the routes? In asynchronous transmission, data is sent in form of byte or character. Five times I sent messages from client to the server and another five-time from server to the client. Waited for more than 15 minutes. Nothing, even one letter, arrived at the other side ! :(

What I get instead was error messages from both projects.
Client:
"The following error occurred: Connection timed out" QNativeSocketEngine::write() was not called in QAbstractSocket::ConnectedState "The following error occurred: Connection timed out"

Server:
Reply got back with no error! QIODevice::write (QTcpSocket): device not open QIODevice::write (QTcpSocket): device not open QIODevice::write (QTcpSocket): device not open QIODevice::write (QTcpSocket): device not open QIODevice::write (QTcpSocket): device not open qt.qpa.mime: Retrying to obtain clipboard. qt.qpa.mime: Retrying to obtain clipboard.

What can I do? :(

[qcoderpro]

@SGaist
I think QNetworkAccessManager is merely responsible for sending the request (or as written in the code geting the request) and since the reply brings no error so apparently there shouldn't be any more worries regarding that. The rest, however, is done by QTCPSoket/Server and other stuff which are connection oriented.

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

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

[SGaist]

You are using your code sequentially and not asynchronously. First understand that.

Use properly signals and slots.

You are also not doing any error checks server side.

It's also not even clear how your are reading and writing to your sockets now.

[qcoderpro]

@SGaist

You are using your code sequentially and not asynchronously.

What do you mean by that? I don't get it!

Use properly signals and slots.
You are also not doing any error checks server side.

This is part of server's code embracing connections as well as error checks:

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

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!";
}

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);
}

void Server::displayError(QAbstractSocket::SocketError socketError) {

    switch (socketError) {
    case QAbstractSocket::RemoteHostClosedError:
        break;
    case QAbstractSocket::HostNotFoundError:
        qInfo() <<"The host was not found. Please check the "
                  "host name and port settings.";
        break;
    case QAbstractSocket::ConnectionRefusedError:
        qInfo() << "The connection was refused by the peer. "
                   "Make sure the server is running, "
                   "and check that the host name and port "
                   "settings are correct.";
        break;
    default:
        qInfo() << "The following error occurred: " + tcpSocket->errorString();
    }
}

What other connections should I add?

It's also not even clear how your are reading and writing to your sockets now.

It's identical to the way both apps are running on the same machine.
It is writeMessage():

void Server::writeMessage()
{
    inOut.startTransaction();

    QString message;
    inOut >> message;

    if (!inOut.commitTransaction())
        setMessage("commitTransaction error");
   else
       setMessage(message);
}

void Server::setMessage(const QString& newMessage)
{
    message += newMessage + '\n';
    emit messageChanged(message);
}

[SGaist]

What is inOut supposed to be ?

[qcoderpro]

@SGaist
This is server's whole header:

#ifndef SERVER_H
#define SERVER_H

#include <QObject>
#include <QAbstractSocket>

class QTcpServer;
class QTcpSocket;
class QNetworkReply;

class Server : public QObject
{
    Q_OBJECT
     Q_PROPERTY(QString message READ getMessage WRITE setMessage NOTIFY messageChanged)

public:
    explicit Server(QObject *parent = nullptr);

    void setMessage(const QString&);
    QString getMessage() const;

public slots:
    void initServer();
    void onNewConnection();
    void displayError(QAbstractSocket::SocketError);
    void sendMessage(const QString&);
    void writeMessage();
   
signals:
    void messageChanged(QString);

private:
    QTcpSocket* tcpSocket { nullptr };
    QTcpServer* tcpServer { nullptr };
    QDataStream inOut;
};
#endif // SERVER_H

And sendMessage's definition:

void Server::sendMessage(const QString& newMessage)
{
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    inOut << newMessage;
    tcpSocket->write(block);
}