QTcpServer -- how to stop client threads - qt

Question

My gui have a two button's, one to start a server & other to stop a server.
Brief :---
Once server is started, on every new client request i will create a new thread & this will handle communication with the client.
Detail :--
When start button is pressed, I am creating an object 'tcpserverobjectWrapper' which creates an another object 'tcpserverobject' this object creats an Qtcpserver.
Now this Qtcpserver is listing for new connection. And when a new connection comes i create an 'TcpSocketThreadWrapperObject' object which
creates a thread & this thread handles communication with client . Also 'tcpserverobject' keeps the list of new client request objects created
'QList<TcpSocketThreadWrapperObject *> TcpSocketThreadWrapperObjectList;' .
I am able to connect to server from telnet clients & it creates new thread for each client & works fine.
When stop button pressed i am able to stop server & client threads.
But i have two problems here :---
1> Everytime client send some data to server. I get this kind of QsocketNotifier. What is this ?
QSocketNotifier: socket notifiers cannot be enabled from another thread
QSocketNotifier: socket notifiers cannot be disabled from another thread
2> If i press stop button on GUI i am able to stop the threads succesfully.
But how to stop the threads & delete the objects created for every client when client send 'STOP command' to server or closes the connection with server ?
I will also have to delete the following objects created on each client request ?
client request --> TcpSocketThreadWrapperObject -- creates --> TcpSocketThreadObject -- creates --> TcpSocketThreadObject
Can someone suggest how to solve above two problems ? Reply on this will be appreciated.
Here is the code :---
================= start & stop buttons handler =====
void MainWindow::on_actionStop_triggered()
{
if(b_threadAlreadyStarted)
{
/* ------------------ Tcp server object ------------------------*/
b_threadAlreadyStarted = false;
delete p_tcpserverobjectWrapper;
/* ------------------ Tcp server object ------------------------*/
}
}
void MainWindow::on_actionStart_triggered()
{
if(!b_threadAlreadyStarted)
{
/* ------------------ Tcp server object ------------------------*/
b_threadAlreadyStarted =true;
p_tcpserverobjectWrapper = new tcpserverobjectWrapper(this,modelCANalyzer);
qDebug() << " \n start ";
/* ------------------ Tcp server object ------------------------*/
}
}
======== tcpserverobjectWrapper class ===============
// Main server object wrapper
class tcpserverobjectWrapper : public QObject
{
Q_OBJECT
public:
explicit tcpserverobjectWrapper(QMainWindow *ptrWidget, QStandardItemModel *modelCANalyzer, QObject *parent=0);
~tcpserverobjectWrapper();
//Device thread object
tcpserverobject *m_tcpserverobject;
};
tcpserverobjectWrapper::tcpserverobjectWrapper(QMainWindow *ptrWidget , QStandardItemModel *modelCANalyzer,QObject *parent) :
QObject(parent)
{
m_tcpserverobject = new tcpserverobject ;
//save model
m_tcpserverobject->modeltable = modelCANalyzer;
m_tcpserverobject->ptrmainwindow = ptrWidget;
qDebug() << "\n tcp server thread started";
}
tcpserverobjectWrapper::~tcpserverobjectWrapper()
{
qDebug() << " \n called delete later on tcpserverobjectWrapper .. !!";
m_tcpserverobject->deleteLater(); // ---------------------> change it to - delete m_tcpserverobject
qDebug() << " \n tcp server object successfully quited .. !! ";
}
========== tcpserverobject object ==================
class tcpserverobject : public QObject
{
Q_OBJECT
public:
explicit tcpserverobject(QObject *parent = 0);
~tcpserverobject();
/*!
Pointer to QStandardItemModel to be used inside - canTableView
*/
QStandardItemModel *modeltable;
//mainwindow pointer
QMainWindow *ptrmainwindow;
// Create list of new -- socket thread wrapper objects
QList<TcpSocketThreadWrapperObject *> TcpSocketThreadWrapperObjectList;
private:
QTcpServer *tcpServer;
signals:
public slots:
void on_newConnection();
};
tcpserverobject::tcpserverobject(QObject *parent) :
QObject(parent), tcpServer(0)
{
tcpServer = new QTcpServer;
// Connect slot of the server
connect(tcpServer, SIGNAL(newConnection()), this, SLOT(on_newConnection()));
//lisen on socket
if (!tcpServer->listen(QHostAddress::LocalHost, SERVER_PORT )) {
qDebug() << "\n returning from server listning error .. !!! ";
return;
}
qDebug() << "\n server listning";
}
tcpserverobject::~tcpserverobject()
{
// to do
while (!TcpSocketThreadWrapperObjectList.isEmpty())
delete TcpSocketThreadWrapperObjectList.takeFirst();
}
void tcpserverobject::on_newConnection()
{
QByteArray block;
block.append(" \n Hello from server .. !!!") ;
QTcpSocket *clientConnection = tcpServer->nextPendingConnection();
connect(clientConnection, SIGNAL(disconnected()),
clientConnection, SLOT(deleteLater()));
// Create new thread for this .. client request ..!!
qDebug() << "\n New connection request ..!!!";
qDebug() << "\n New client from:" << clientConnection->peerAddress().toString();
clientConnection->write(block);
clientConnection->flush();
// create new tcp object
TcpSocketThreadWrapperObject* TcpSocketThreadWrapperObjectPtr = new TcpSocketThreadWrapperObject(clientConnection);
// Append object to the list
TcpSocketThreadWrapperObjectList.append(TcpSocketThreadWrapperObjectPtr);
}
============ TcpSocketThreadWrapperObject ==============
// Main device thread object
class TcpSocketThreadWrapperObject : public QObject
{
Q_OBJECT
public:
explicit TcpSocketThreadWrapperObject(QTcpSocket *m_pTcpSocket , QObject *parent = 0);
~TcpSocketThreadWrapperObject();
/*!
pointer for write thread
*/
QThread m_TcpSocketRWThread;
/// pointer to the socketthread object
class TcpSocketThreadObject *m_pTcpSocketThreadObject;
signals:
public slots:
};
// constructor for the deviceThreadObject
TcpSocketThreadWrapperObject::TcpSocketThreadWrapperObject(QTcpSocket *m_pTcpSocket , QObject *parent) :
QObject(parent)
{
m_pTcpSocketThreadObject = new TcpSocketThreadObject(m_pTcpSocket);
//set flag for event loop -- make while(1)
m_pTcpSocketThreadObject->m_bQuit = false;
// connect the signal & slot
connect(&m_TcpSocketRWThread,SIGNAL(started()),m_pTcpSocketThreadObject,SLOT(dowork_socket()));
// Move thread to object
m_pTcpSocketThreadObject->moveToThread(&m_TcpSocketRWThread);
//Start the thread
m_TcpSocketRWThread.start();
}
TcpSocketThreadWrapperObject::~TcpSocketThreadWrapperObject()
{
//set flag for event loop -- make while(0)
m_pTcpSocketThreadObject->m_bQuit = false;
// Wait for the thread to terminate
m_TcpSocketRWThread.quit();
m_TcpSocketRWThread.wait();
// Delete the object
m_pTcpSocketThreadObject->deleteLater();
qDebug() << "\n deleted - TcpSocketThreadWrapperObject";
}
======== TcpSocketThreadObject object ========
class TcpSocketThreadObject : public QObject
{
Q_OBJECT
public:
explicit TcpSocketThreadObject(QTcpSocket *m_pTcpSocketTemp , QObject *parent = 0);
~TcpSocketThreadObject();
/*!
Pointer to TCP socket -- created by the server
*/
QTcpSocket *m_pclientConnectionSocket;
/*!
Termination control main thread
*/
volatile bool m_bQuit;
signals:
public slots:
void dowork_socket();
};
// constructor for the deviceThreadObject
TcpSocketThreadObject::TcpSocketThreadObject(QTcpSocket *m_pTcpSocketTemp , QObject *parent) :
QObject(parent)
{
m_pclientConnectionSocket = m_pTcpSocketTemp;
// todo
}
TcpSocketThreadObject::~TcpSocketThreadObject()
{
// todo
}
void TcpSocketThreadObject::dowork_socket()
{
QByteArray block;
block.append(" \n hi again .. !!!") ;
// Write to socket
m_pclientConnectionSocket->write(block);
m_pclientConnectionSocket->flush();
// Close socket
m_pclientConnectionSocket->disconnectFromHost();
qDebug() << "\n entring loop of socket thread ..!!!";
while(!m_bQuit)
{
// while loop --> send/rx command from client
}
}
======= output of one client connected to server =====
New connection request ..!!!
New client from: "127.0.0.1"
QSocketNotifier: socket notifiers cannot be enabled from another thread
QSocketNotifier: socket notifiers cannot be disabled from another thread
entring loop of socket thread ..!!!

Answer 1

I think the simplest solution to all of this is to stop using QThread.
QTcpSocket and QTcpServer are both asynchronous, so when you receive a connection, you only need to create a class to wrap the QTcpSocket and this class handles the reading of the data, having connected the QTcpSocket signals to the class's slots.
If you're getting a lot of connections, then you'll be creating lots of threads. More threads than processor cores is just a waste of time.
If each connection is requesting a lot of work to be done by the server, you can then create separate worker objects and move those to a different thread, but overall, I recommend that you do not use separate threads for QTcpServer and QTcpSockets.