QT TcpServer detecting input and correctly replying

rktech

Hi,
I have a problem. I am trying to implement TcpServer correctly reply on message from qtcpsocket client. But my implementation on ReadyRead don´t work. Can I ask where is problem?
myserver.cpp

#include "myserver.h"

MyServer::MyServer(QObject *parent) :
    QObject(parent)
{
    server = new QTcpServer(this);

    connect(server, SIGNAL(newConnection()), this, SLOT(newConnection()));

    if(!server->listen(QHostAddress::Any, 1234))
    {
        qDebug() << "Server could not start!";
    }
    else
    {
        qDebug() << "Server started!";
    }
}

void MyServer::newConnection()
{

    QTcpSocket *socket = server->nextPendingConnection();
    connect(socket, SIGNAL(readyRead()), this, SLOT(onReadyRead()));
/*
    //socket->write("hello client\r\n");
    //socket->flush();

    socket->waitForBytesWritten(3000);

    socket->close();*/
}
void MyServer::onReadyRead()
{
    QTcpSocket* sender = static_cast<QTcpSocket*>(QObject::sender());
    QByteArray datas = sender->readAll();
    for (QTcpSocket* socket : _sockets) {
        if (socket != sender){
        QString a = QString::fromStdString(datas.toStdString());
        QString com = a.mid(0,3);
        //41
        //socket->write(QByteArray::fromStdString(/*sender->peerAddress().toString().toStdString() + ": " +*/ a.mid(0,3).toStdString()));
        socket->write("SA");
        socket->flush();
        socket->waitForBytesWritten(5000);
        socket->close();
    }
}
}

myserver.h

#ifndef MYSERVER_H
#define MYSERVER_H

#include <QObject>
#include <QDebug>
#include <QTcpServer>
#include <QTcpSocket>
#include <QString>
class MyServer : public QObject
{
    Q_OBJECT
public:
    explicit MyServer(QObject *parent = 0);
    
signals:
    
public slots:
    void newConnection();
    void onReadyRead();

private:
    QTcpServer *server;
    QList<QTcpSocket*>  _sockets;
    QString a;
    QString com;
    QTcpSocket *socket;
};

#endif // MYSERVER_H

main.cpp

#include "mainwindow.h"
#include <QApplication>
#include "myserver.h"
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    MyServer S;
    return a.exec();
}

mainwindow.cpp and mainwindow.h is not edited.
Thanks
rktech

Christian Ehrlicher

@rktech said in QT TcpServer detecting input and correctly replying:

But my implementation on ReadyRead don´t work.

What exactly don't work?

for (QTcpSocket* socket : _sockets) {

Why do you do this? Just dynamic_cast the sender, check for != nullptr and use this QTcpSocket.

rktech

My client didn´t have any response. Can you fix my whole code? I don´t know what do you mean by nullptr.
thanks
rktech

SGaist

Hi,

Based on your code, _sockets is never modified, neither on a new connection nor when a connection is closed.

Christian Ehrlicher

@rktech said in QT TcpServer detecting input and correctly replying:

Can you fix my whole code?

I'm not here to fix code for anyone, just for helping.

First I would not directly close the connection and don't use waitForBytesWritten() but signals/slots.

I don´t know what do you mean by nullptr.

See what dynamic_cast is doing: https://en.cppreference.com/w/cpp/language/dynamic_cast or qobject_cast which does work here too: https://doc.qt.io/qt-5/qobject.html#qobject_cast

Pablo J. Rogina

@rktech have you checked the Fortune server example?

rktech

@pablo-j-rogina there is nothing about reading input from client.
@Christian-Ehrlicher I read that, but i don´t know what i am doing wrong.

Christian Ehrlicher

As @SGaist pointed out you don't fill _sockets anywhere and as I pointed out you don't need to search the socket in _sockets at all since you already cast QObject::sender() to the correct QTcpSocket although qobject_cast or dynamic_cast should be used instead static_cast