QDataSream: No Device

Hi. I'm writing a few small test socket programs using Qt libraries without using the event loop (i.e. no Signals and Slots). Here is the source code for a small server:

#include <QtNetwork>
#include <iostream>
#include <qdatastream.h>

int main(int *argc, char *argv[]){

QTcpServer server;
QTcpSocket *socket;
server.listen(QHostAddress::LocalHost,8000);
bool timeout;
server.waitForNewConnection(50000,&timeout);
socket=server.nextPendingConnection();
QDataStream in(socket);
in.setVersion(QDataStream::Qt_4_0);
int number;
in>>number;
std::cout<<number<<std::endl;

}

and a simple client:

#include <QtNetwork>
#include <iostream>
#include <qdatastream.h>

int main(int *argc, char *argv[]){

QTcpSocket socket;
socket.connectToHost(QHostAddress::LocalHost,8000) ;
if (!socket.waitForConnected(5000)) {

std::cout<<"Cannot connect to GUI."<<std::endl;
return 0;

}
QDataStream out(&socket);
out.setVersion(QDataStream::Qt_4_0);
out<<1;

}

when I run the server (receiving data) and then the client, the server displays the message "QDataStream: No device" followed by a zero. What am I doing wrong? thanks.

Edit: I forgot to note that the client displays the error message "Cannot connect to GUI"

QTcpServer needs an event loop running. So does QTcpSocket.

Actually, the QT documentation site says that both QTcpSocket and QTcpServer can be used without an event loop.

You must initialize timeout to false (see here) and you have to invoke QIODevice::waitForReadyRead() and QIODevice::waitForBytesWritten() in proper places to wait for data to be passed over the network.

Awesome, thanks a lot. I would never have been able to locate that QT bug. I still have a little trouble with the two other blocking calls because I get a segmentation fault. Do you have any idea what could be causing this?

Most segfaults are caused by dangling pointers. Use a debugger to see where it crashes and what parameters were passed to functions on the call stack.