QtNetwork: incomingConnection not triggered

[calmstack]

Hello,

I am quite new in Qt and trying for hours now to solve an issue on QtNetwork, working with QTcpSocket.

I try to establish a simple server/client connection for a small game and while my clients successfuly "connect" to the server (telnet works for example), the incomingConnection method is never triggered.

The main.cpp part starting the server :

Server *server = new Server(host, port, nb_players);
server->start();
std::cout << "Waiting for " << nb_players << " players to join..." << std::endl;

while (static_cast<int>(server->getClients().size()) < nb_players);

std::cout << "Perfect, " << nb_players << " joined !" << std::endl;

Here is my Server.h :

class Server : public QTcpServer {
    Q_OBJECT

public:
    Server(std::string listen_host, int listen_port, int max_clients, QObject *parent = nullptr);
    void start(void);
    void stop(void);
    std::vector<Client*> getClients();

protected:
    void incomingConnection(qintptr socketDescriptor) Q_DECL_OVERRIDE;

private slots:
    void readyRead();
    void disconnected();

private:
    std::map<QTcpSocket*, Client> clients;
    QString listen_host;
    int listen_port;
    int max_clients;
};

My Server.cpp :

Server::Server(std::string listen_host, int listen_port, int max_clients, QObject *parent)
    : QTcpServer(parent)
{
    this->listen_host = QString::fromUtf8(listen_host.c_str());
    this->listen_port = listen_port;
    this->max_clients = max_clients;
}

void Server::start(void)
{
    QHostAddress address;
    address.setAddress(this->listen_host);
    listen(address, (qint16)this->listen_port);
}

void Server::stop(void) { close(); }

void Server::incomingConnection(qintptr socketDescriptor)
{
    QTcpSocket *socket_client = new QTcpSocket(this);
    socket_client->setSocketDescriptor(socketDescriptor);

    if (static_cast<int>(this->clients.size()) >= max_clients) {
        socket_client->disconnect();
        qDebug() << "No additional client accepted";
        return;
    }

    Client client = Client(socket_client);
    this->clients.insert(std::pair<QTcpSocket*, Client>(socket_client, client));

    connect(socket_client, SIGNAL(readyRead()), this, SLOT(readyRead()));
    connect(socket_client, SIGNAL(disconnected()), this, SLOT(disconnected()));
}

void Server::readyRead()
{
    QTcpSocket *socket_client = (QTcpSocket*)sender();
    Client client = clients.find(socket_client)->second;
    // other stuff
}

void Server::disconnected()
{
    QTcpSocket *socket_client = (QTcpSocket*)sender();
    Client client = clients.find(socket_client)->second;
    // other stuff
    clients.erase(socket_client);
}

std::vector<Client*> Server::getClients()
{
    std::vector<Client*> ptr_clients;
    std::map<QTcpSocket*, Client>::iterator it;
    for ( it = this->clients.begin(); it != this->clients.end(); it++ )
        ptr_clients.push_back(&it->second);
    return ptr_clients;
}

Could you provide me with any help for debugging this problem ?

Thank you.

[Bonnie]

I think your while statement in main.cpp blocks the main thread.
If you want do it in the blocking way, try QTcpServer::waitForNewConnection.
(BTW, do you have QCoreApplication / QApplication in the main.cpp ?)
But it is recommended to use the non-blocking / asynchronous way: signals.
Also I don't see the necessity for you to reimplement incomingConnection.
You can just do the Client creating from nextPendingConnection() as the normal way.

[Christian Ehrlicher]

@Bonnie said in QtNetwork: incomingConnection not triggered:

I think

Why only think? That's the reason.

@calmstack don't block the event loop then all is working fine.

[calmstack]

@Bonnie Thank you very much for the precisions, that was it.

Yes I have a QCoreApplication.

Solving my problem using :

while ((int)server->getClients().size() < nb_players)
        server->waitForNewConnection();

[jsulm]

@calmstack said in QtNetwork: incomingConnection not triggered:

while ((int)server->getClients().size() < nb_players)
server->waitForNewConnection();

There is no need for this at all if you use Qt in the way it is supposed to be used.
Qt is asynchronous. Just connect a slot to https://doc.qt.io/qt-5/qtcpserver.html#newConnection

[calmstack]

@jsulm Yes I've finished by choosing the QThread way.

[jsulm]

@calmstack said in QtNetwork: incomingConnection not triggered:

QThread

Why QThread?! As I said: Qt is asynchronous.

[calmstack]

@jsulm Isn't it what the official documentation recommends ?

[SGaist]

Hi,

@calmstack said in QtNetwork: incomingConnection not triggered:

@jsulm Isn't it what the official documentation recommends ?

No, it's one usage example. You have the same example without threads.