Hi All,
I have a problem with Qt's sockets. I have a server application that listens for incoming connections and a client application that connects to the host. So far so good. I'm able to create the connection and send/receive data. The client sends a huge amount of data (in blocks) to the server, while keeping up the connection.
I encountered a problem that drives me crazy since a few days now, and I haven't found any solution yet. I tried to narrow down the problem to minimum and to have an example code for showing.
At some point there is a memory issue, but I can't figure out what causes it:
std::bad_alloc at memory location 0x0019d434
Here is the code example
Server Application:
TcpServer
#ifndef TCPSERVER_H
#define TCPSERVER_H
#include "serversocket.h"
#include <QTcpServer>
#include <QHostAddress>
{
Q_OBJECT
public:
{
{
exit(-1);
}
};
protected:
virtual void incomingConnection ( int socketDescriptor )
{
ServerSocket *socket = new ServerSocket(this);
socket->setSocketDescriptor(socketDescriptor);
connect(socket, SIGNAL(readyRead()), socket, SLOT(readBlockData()));
};
};
#endif // TCPSERVER_H
#ifndef TCPSERVER_H
#define TCPSERVER_H
#include "serversocket.h"
#include <QTcpServer>
#include <QHostAddress>
class TcpServer : public QTcpServer
{
Q_OBJECT
public:
TcpServer ( QObject * parent = 0 ) : QTcpServer(parent)
{
if (!this->listen( QHostAddress::LocalHost, 2688))
{
exit(-1);
}
};
protected:
virtual void incomingConnection ( int socketDescriptor )
{
ServerSocket *socket = new ServerSocket(this);
socket->setSocketDescriptor(socketDescriptor);
connect(socket, SIGNAL(readyRead()), socket, SLOT(readBlockData()));
};
};
#endif // TCPSERVER_H
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ServerSocket
#ifndef SERVERSOCKET_H
#define SERVERSOCKET_H
#include <QTcpSocket>
#include <QHostAddress>
#include <QDataStream>
#include <iostream>
#include <cstring>
{
Q_OBJECT
public:
{
this->blockSize = 0;
};
public slots:
void readBlockData()
{
if (this->blockSize == 0)
{
if (this->bytesAvailable() < (int)sizeof(quint32))
return;
in >> this->blockSize;
}
if (this->bytesAvailable() < this->blockSize)
return;
char* blockData = new char[this->blockSize];
in >> blockData;
std::cout << (int)byteArray.size() << " - " << this->bytesAvailable() << "\n";
this->blockSize = 0;
delete[] blockData;
};
private:
quint32 blockSize;
};
#endif // SERVERSOCKET_H
#ifndef SERVERSOCKET_H
#define SERVERSOCKET_H
#include <QTcpSocket>
#include <QHostAddress>
#include <QDataStream>
#include <iostream>
#include <cstring>
class ServerSocket : public QTcpSocket
{
Q_OBJECT
public:
ServerSocket ( QObject * parent = 0 ) : QTcpSocket(parent)
{
this->blockSize = 0;
};
public slots:
void readBlockData()
{
QDataStream in(this);
in.setVersion(QDataStream::Qt_4_7);
if (this->blockSize == 0)
{
if (this->bytesAvailable() < (int)sizeof(quint32))
return;
in >> this->blockSize;
}
if (this->bytesAvailable() < this->blockSize)
return;
char* blockData = new char[this->blockSize];
in >> blockData;
QByteArray byteArray(blockData);
std::cout << (int)byteArray.size() << " - " << this->bytesAvailable() << "\n";
this->blockSize = 0;
delete[] blockData;
};
private:
quint32 blockSize;
};
#endif // SERVERSOCKET_H
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Main
#include <QtCore/QCoreApplication>
#include "tcpserver.h"
int main(int argc, char *argv[])
{
TcpServer *server = new TcpServer();
return a.exec();
}
#include <QtCore/QCoreApplication>
#include "tcpserver.h"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
TcpServer *server = new TcpServer();
return a.exec();
}
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Client application:
ClientSocket
#ifndef CLIENTSOCKET_H
#define CLIENTSOCKET_H
#include <QTcpSocket>
#include <QHostAddress>
#include <QDataStream>
#include <iostream>
#include <cstring>
{
Q_OBJECT
public:
{
if (!this->waitForConnected(3000))
exit(-1);
};
void writeBlockData(const char* blockData, size_t size)
{
out << (quint32)0;
out << dataArray;
out.device()->seek(0);
out << (quint32)(block.size() - sizeof(quint32));
this->write(block);
this->flush();
this->waitForBytesWritten(-1);
};
};
#endif // CLIENTSOCKET_H
#ifndef CLIENTSOCKET_H
#define CLIENTSOCKET_H
#include <QTcpSocket>
#include <QHostAddress>
#include <QDataStream>
#include <iostream>
#include <cstring>
class ClientSocket : public QTcpSocket
{
Q_OBJECT
public:
ClientSocket ( QObject * parent = 0 ) : QTcpSocket(parent)
{
connectToHost(QHostAddress::LocalHost, 2688);
if (!this->waitForConnected(3000))
exit(-1);
};
void writeBlockData(const char* blockData, size_t size)
{
QByteArray dataArray((char*) blockData, size);
QByteArray block;
QDataStream out(&block, QIODevice::WriteOnly);
out.setVersion(QDataStream::Qt_4_7);
out << (quint32)0;
out << dataArray;
out.device()->seek(0);
out << (quint32)(block.size() - sizeof(quint32));
this->write(block);
this->flush();
this->waitForBytesWritten(-1);
};
};
#endif // CLIENTSOCKET_H
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Main
#include <QtCore/QCoreApplication>
#include "clientsocket.h"
int main(int argc, char *argv[])
{
unsigned int size = 1000*1000*3;
char *data = new char[size];
for (int i = 0; i < size; i++)
{
data[i] = 'q';
}
ClientSocket client;
for (int blocks = 0; blocks < 2000; blocks++)
{
client.writeBlockData(data, size);
std::cout << blocks << std::endl;
}
delete[] data;
return a.exec();
}
#include <QtCore/QCoreApplication>
#include "clientsocket.h"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
unsigned int size = 1000*1000*3;
char *data = new char[size];
for (int i = 0; i < size; i++)
{
data[i] = 'q';
}
ClientSocket client;
for (int blocks = 0; blocks < 2000; blocks++)
{
client.writeBlockData(data, size);
std::cout << blocks << std::endl;
}
delete[] data;
return a.exec();
}
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I was testing the code on Windows 7 with Qt 4.7 using visual studio 2008.
1.
The first problem is not really a problem, but more something that I found worth mentioning and I was wondering if someone else experienced something similar.
When running the code in Debug mode after reading data from the socket server, the buffer seems not to be cleared. The memory keeps increasing until there is nothing left to be allocated. This seems not to be the case for compiling and running the code in Release mode.
2.
But weird is, that even in Release mode, after the same number of received blocks, I get the above mentioned exception and the server application crashes.
Thank you!!!
QTcpSocket - memory allocation problem
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