My QTCPServer crashes

[Mr_Burns]

Hi everybody,

I'm new to Qt and this forum. After my first steps in the last few weeks with Qt, I tried to write a server which can handle multiple clients. The basis for my program is "Multi client server without threading" of this site.

My methode Server::start() ist connected with a button, also the methode Server::stop(). When I start my server all works fine, but when I try to stop my server and restart it again with the buttons, my Server crashes as soon as I want to connect with the client. Has anybody of you an idea for a solution for my problem?

Here my code:

// network.h
#ifndef NETWORK_H
#define NETWORK_H
 
#include <QTcpServer>
#include <QTcpSocket>
#include <QHostAddress>
#include <QList>
#include <QHash>
#include <QBuffer>
#include "mainwindow.h"
 
class Server : public QTcpServer {
	Q_OBJECT
 
protected:
	void sendHello(QTcpSocket *client);
 
protected slots:
	void handleNewConnection();
	void clientDisconnected();
	void start(int port = 10002);
	void stop();
	void read();
 
private:
	QList<QTcpSocket *> clientConnections;
	QHash<QTcpSocket*, QBuffer*> buffers;
 
public:
	explicit Server();
	~Server();
};
 
 
#endif // NETWORK_H

// network.h
#ifndef NETWORK_H
#define NETWORK_H

#include <QTcpServer>
#include <QTcpSocket>
#include <QHostAddress>
#include <QList>
#include <QHash>
#include <QBuffer>
#include "mainwindow.h"

class Server : public QTcpServer {
	Q_OBJECT

protected:
	void sendHello(QTcpSocket *client);

protected slots:
	void handleNewConnection();
	void clientDisconnected();
	void start(int port = 10002);
	void stop();
	void read();

private:
	QList<QTcpSocket *> clientConnections;
	QHash<QTcpSocket*, QBuffer*> buffers;

public:
	explicit Server();
	~Server();
};


#endif // NETWORK_H

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// network.c
#include "network.h"
 
Server::Server() {
}
 
Server::~Server() {
	stop();
}
 
void Server::stop() {
	close();
	qDeleteAll(clientConnections);
}
 
void Server::start(int port) {
	if(!listen(QHostAddress::Any, port)) {
		return;
	}
	connect(this, SIGNAL(newConnection()), this, SLOT(handleNewConnection()));
}
 
void Server::handleNewConnection() {
	while (hasPendingConnections()) {
		QTcpSocket *client = nextPendingConnection();
		QBuffer* buffer = new QBuffer(this);
		buffer->open(QIODevice::ReadWrite);
		buffers.insert(client, buffer);
		connect(client, SIGNAL(disconnected()), this, SLOT(clientDisconnected()));
		connect(client, SIGNAL(readyRead()), this, SLOT(read()));
		clientConnections.append(client);
 
		sendHello(client);
	}
}
 
void Server::clientDisconnected() {
	QTcpSocket *client = qobject_cast<QTcpSocket *>(sender());
 
	if(!client) return;
 
	clientConnections.removeAll(client);
	client->deleteLater();
}
 
void Server::sendHello(QTcpSocket *client) {
	if(!client) return;
	client->write("Hello\n");
}
 
void Server::read() {
	QTcpSocket *client = qobject_cast<QTcpSocket *>(sender());
	QBuffer* buffer = buffers.value(client);
 
	if(!client) return;
 
	qint64 bytes = buffer->write(client->readAll());
	buffer->seek(buffer->pos() - bytes);
	while (buffer->canReadLine()) {
 
		QByteArray line = buffer->readLine();
 
		switch(line[0]) {
		case 'a' : client->write(line);
			break;
		}
	}
}

// network.c
#include "network.h"

Server::Server() {
}

Server::~Server() {
	stop();
}

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

void Server::start(int port) {
	if(!listen(QHostAddress::Any, port)) {
		return;
	}
	connect(this, SIGNAL(newConnection()), this, SLOT(handleNewConnection()));
}

void Server::handleNewConnection() {
	while (hasPendingConnections()) {
		QTcpSocket *client = nextPendingConnection();
		QBuffer* buffer = new QBuffer(this);
		buffer->open(QIODevice::ReadWrite);
		buffers.insert(client, buffer);
		connect(client, SIGNAL(disconnected()), this, SLOT(clientDisconnected()));
		connect(client, SIGNAL(readyRead()), this, SLOT(read()));
		clientConnections.append(client);

		sendHello(client);
	}
}

void Server::clientDisconnected() {
	QTcpSocket *client = qobject_cast<QTcpSocket *>(sender());

	if(!client) return;

	clientConnections.removeAll(client);
	client->deleteLater();
}

void Server::sendHello(QTcpSocket *client) {
	if(!client) return;
	client->write("Hello\n");
}

void Server::read() {
	QTcpSocket *client = qobject_cast<QTcpSocket *>(sender());
	QBuffer* buffer = buffers.value(client);

	if(!client) return;

	qint64 bytes = buffer->write(client->readAll());
	buffer->seek(buffer->pos() - bytes);
	while (buffer->canReadLine()) {

		QByteArray line = buffer->readLine();

		switch(line[0]) {
		case 'a' : client->write(line);
			break;
		}
	}
}

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Thank you in advance.