Write to Threaded Server

[numbat]

Why do you call disconnectFromHost if you want a reply?

[Suncell]

ohh sure - but i fixed it already - this i shouldn't do of course. But it doesn't work anyway :-?

tcpsocket.cpp

CTcpSocket::CTcpSocket(int socketDescriptor, QObject *parent)
: QObject(parent)
, m_socketDescriptor(socketDescriptor)
{
	m_tcpSocket = new QTcpSocket();
 
	if (!m_tcpSocket->setSocketDescriptor(m_socketDescriptor)) {
		qDebug() << m_tcpSocket->error();
		return;
	}
 
	connect(m_tcpSocket, SIGNAL(readyRead()), SLOT(readData()));
}
 
 
void CTcpSocket::readData()
{
	//ToDo Implement reading Data
	qDebug() << "try to read";
	//m_tcpSocket->waitForReadyRead(10000);
}
 
 
void CTcpSocket::writeData(QString txt)
{
	qDebug() << "try to write";
 
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_4_0);
    out << (quint16)0;
    out << txt;
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));
 
    m_tcpSocket->write(block);
 
    m_tcpSocket->waitForBytesWritten(10000);
}

CTcpSocket::CTcpSocket(int socketDescriptor, QObject *parent)
: QObject(parent)
, m_socketDescriptor(socketDescriptor)
{
	m_tcpSocket = new QTcpSocket();

	if (!m_tcpSocket->setSocketDescriptor(m_socketDescriptor)) {
		qDebug() << m_tcpSocket->error();
		return;
	}

	connect(m_tcpSocket, SIGNAL(readyRead()), SLOT(readData()));
}


void CTcpSocket::readData()
{
	//ToDo Implement reading Data
	qDebug() << "try to read";
	//m_tcpSocket->waitForReadyRead(10000);
}


void CTcpSocket::writeData(QString txt)
{
	qDebug() << "try to write";

    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_4_0);
    out << (quint16)0;
    out << txt;
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));

    m_tcpSocket->write(block);

    m_tcpSocket->waitForBytesWritten(10000);
}

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[tbscope]

One reason you're not being able to read is because there's nothing to read.
Are you sure you are receiving data? Are you sure that what you send is correct?

[Suncell]

There is something to read for sure - I've a working not threaded server. There the message arrives.

Client is like this:

InstructionGen::InstructionGen(..)
{
...
socket = new QTcpSocket(this);
...
socket->connectToHost(server->text(), port->value());
...
}
 
void InstructionGen::sendInstruction()
{
	socket->write(prefix->text().toLatin1() + message->text().toLatin1() + "\n");
	log_stat->append((prefix->text().toLatin1() + message->text().toLatin1() + "\n").simplified());
	message->clear();
}

InstructionGen::InstructionGen(..)
{
...
socket = new QTcpSocket(this);
...
socket->connectToHost(server->text(), port->value());
...
}

void InstructionGen::sendInstruction()
{
	socket->write(prefix->text().toLatin1() + message->text().toLatin1() + "\n");
	log_stat->append((prefix->text().toLatin1() + message->text().toLatin1() + "\n").simplified());
	message->clear();
}

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[tbscope]

Where do you call void InstructionGen::sendInstruction() in your server?

Edit: and you don't need to use threads and the socket's blocking functions.

[Suncell]

InstructionGen is the client, which should send data to the server.

Thx for the hint with the blocking functions... but should work anyway - am I right?

[tbscope]

You have lost me completely.
Can you post the complete code please?

[Suncell]

Okay: server is complete.

Now the Client: its actual the ChatSample Client in a slightly different form.

Client:

main.cpp

#include <QApplication>
#include "instructiongen.h"
 
int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
	InstructionGen generator;
	generator.show();
	return a.exec();
}

#include <QApplication>
#include "instructiongen.h"

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
	InstructionGen generator;
	generator.show();
	return a.exec();
}

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instructiongen.cpp

#include "instructiongen.h"
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QGridLayout>
#include <QPushButton>
#include <QTextEdit>
#include <QLabel>
#include <QLineEdit>
#include <QTcpSocket>
#include <QBuffer>
#include <QSpinBox>
#include <QErrorMessage>
 
static const quint16 DEFAULT_PORT = 15001;
 
InstructionGen::InstructionGen(QWidget* parent, Qt::WFlags flags)
: QWidget(parent, flags)
{
	QVBoxLayout* main	= new QVBoxLayout(this);
	QGridLayout* top	= new QGridLayout;
	QHBoxLayout* bottom	= new QHBoxLayout;
 
	QLabel* label	= new QLabel("Server:", this);
	server			= new QLineEdit(this);
	port			= new QSpinBox(this);
	conn			= new QPushButton("Connect", this);
	port->setRange(1, 32767);
	port->setValue(DEFAULT_PORT);
	server->setText("localhost");
	top->addWidget(label, 0, 0);
	top->addWidget(server, 0, 1);
	top->addWidget(port, 0, 2);
 
	label	= new QLabel("Prefix:", this);
	prefix	= new QLineEdit(this);
	prefix->setText("sim.");
	top->addWidget(label, 1, 0);
	top->addWidget(prefix, 1, 1);
	top->addWidget(conn, 1, 2);
 
	log_stat	= new QTextEdit(this);
	log_stat->setReadOnly(true);
 
	label	= new QLabel("Instruction:", this);
	message	= new QLineEdit(this);
	send	= new QPushButton("Send", this);
	send->setDefault(true);
	bottom->addWidget(label);
	bottom->addWidget(message);
	bottom->addWidget(send);
 
	main->addLayout(top);
	main->addWidget(log_stat);
	main->addLayout(bottom);
	setLayout(main);
 
	buffer = new QBuffer(this);
	socket = new QTcpSocket(this);
	buffer->open(QIODevice::ReadWrite);
 
	connect(message, SIGNAL(returnPressed()), SLOT(sendInstruction()));
	connect(send, SIGNAL(clicked()), SLOT(sendInstruction()));
	connect(conn, SIGNAL(clicked()), SLOT(toggleConnection()));
 
	connect(socket, SIGNAL(connected()), SLOT(setConnected()));
	connect(socket, SIGNAL(disconnected()), SLOT(setDisconnected()));
	connect(socket, SIGNAL(readyRead()), SLOT(receiveMessage()));
 
	setDisconnected();
}
 
InstructionGen::~InstructionGen()
{
	buffer->close();
}
 
void InstructionGen::setConnected()
{
	port->setEnabled(false);
	server->setEnabled(false);
	prefix->setEnabled(true);
	message->setEnabled(true);
	log_stat->setEnabled(true);
	log_stat->clear();
	send->setEnabled(true);
	conn->setText("Disconnect");
}
 
void InstructionGen::setDisconnected()
{
	port->setEnabled(true);
	server->setEnabled(true);
	prefix->setEnabled(false);
	message->setEnabled(false);
	log_stat->setEnabled(false);
	send->setEnabled(false);
	conn->setText("Connect");
}
 
void InstructionGen::toggleConnection()
{
	if (socket->state() == QAbstractSocket::UnconnectedState)
	{
		socket->connectToHost(server->text(), port->value());
	}
	else
	{
		socket->disconnectFromHost();
	}
}
 
void InstructionGen::sendInstruction()
{
	socket->write(prefix->text().toLatin1() + message->text().toLatin1() + "\n");
	log_stat->append((prefix->text().toLatin1() + message->text().toLatin1() + "\n").simplified());
	message->clear();
}
 
void InstructionGen::receiveMessage()
{
	// missing some checks for returns values for the sake of simplicity
	qint64 bytes = buffer->write(socket->readAll());
	// go back as many bytes as we just wrote so that it can be read
	buffer->seek(buffer->pos() - bytes);
	// read only full lines, line by line
	while (buffer->canReadLine())
	{
		QString line = buffer->readLine();
		log_stat->append("received: "+line.simplified());
	}
}

#include "instructiongen.h"
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QGridLayout>
#include <QPushButton>
#include <QTextEdit>
#include <QLabel>
#include <QLineEdit>
#include <QTcpSocket>
#include <QBuffer>
#include <QSpinBox>
#include <QErrorMessage>

static const quint16 DEFAULT_PORT = 15001;

InstructionGen::InstructionGen(QWidget* parent, Qt::WFlags flags)
: QWidget(parent, flags)
{
	QVBoxLayout* main	= new QVBoxLayout(this);
	QGridLayout* top	= new QGridLayout;
	QHBoxLayout* bottom	= new QHBoxLayout;

	QLabel* label	= new QLabel("Server:", this);
	server			= new QLineEdit(this);
	port			= new QSpinBox(this);
	conn			= new QPushButton("Connect", this);
	port->setRange(1, 32767);
	port->setValue(DEFAULT_PORT);
	server->setText("localhost");
	top->addWidget(label, 0, 0);
	top->addWidget(server, 0, 1);
	top->addWidget(port, 0, 2);

	label	= new QLabel("Prefix:", this);
	prefix	= new QLineEdit(this);
	prefix->setText("sim.");
	top->addWidget(label, 1, 0);
	top->addWidget(prefix, 1, 1);
	top->addWidget(conn, 1, 2);

	log_stat	= new QTextEdit(this);
	log_stat->setReadOnly(true);

	label	= new QLabel("Instruction:", this);
	message	= new QLineEdit(this);
	send	= new QPushButton("Send", this);
	send->setDefault(true);
	bottom->addWidget(label);
	bottom->addWidget(message);
	bottom->addWidget(send);

	main->addLayout(top);
	main->addWidget(log_stat);
	main->addLayout(bottom);
	setLayout(main);

	buffer = new QBuffer(this);
	socket = new QTcpSocket(this);
	buffer->open(QIODevice::ReadWrite);

	connect(message, SIGNAL(returnPressed()), SLOT(sendInstruction()));
	connect(send, SIGNAL(clicked()), SLOT(sendInstruction()));
	connect(conn, SIGNAL(clicked()), SLOT(toggleConnection()));

	connect(socket, SIGNAL(connected()), SLOT(setConnected()));
	connect(socket, SIGNAL(disconnected()), SLOT(setDisconnected()));
	connect(socket, SIGNAL(readyRead()), SLOT(receiveMessage()));

	setDisconnected();
}

InstructionGen::~InstructionGen()
{
	buffer->close();
}

void InstructionGen::setConnected()
{
	port->setEnabled(false);
	server->setEnabled(false);
	prefix->setEnabled(true);
	message->setEnabled(true);
	log_stat->setEnabled(true);
	log_stat->clear();
	send->setEnabled(true);
	conn->setText("Disconnect");
}

void InstructionGen::setDisconnected()
{
	port->setEnabled(true);
	server->setEnabled(true);
	prefix->setEnabled(false);
	message->setEnabled(false);
	log_stat->setEnabled(false);
	send->setEnabled(false);
	conn->setText("Connect");
}

void InstructionGen::toggleConnection()
{
	if (socket->state() == QAbstractSocket::UnconnectedState)
	{
		socket->connectToHost(server->text(), port->value());
	}
	else
	{
		socket->disconnectFromHost();
	}
}

void InstructionGen::sendInstruction()
{
	socket->write(prefix->text().toLatin1() + message->text().toLatin1() + "\n");
	log_stat->append((prefix->text().toLatin1() + message->text().toLatin1() + "\n").simplified());
	message->clear();
}

void InstructionGen::receiveMessage()
{
	// missing some checks for returns values for the sake of simplicity
	qint64 bytes = buffer->write(socket->readAll());
	// go back as many bytes as we just wrote so that it can be read
	buffer->seek(buffer->pos() - bytes);
	// read only full lines, line by line
	while (buffer->canReadLine())
	{
		QString line = buffer->readLine();
		log_stat->append("received: "+line.simplified());
	}
}

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[tbscope]

Here's your problem

connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));

connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));

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Do you understand why?

If you want to keep it simple, I've just added an example to the wiki on how to do all this without using threads.
A lot of people seem to think they need threads for some reason.
http://www.qtcentre.org/wiki/index.p...ithout_threads

[Suncell]

Outsch yeah - thx.

And I need to loop in the run method - right?

Why isn't a thread necessary. The program will receive tons of data out of a medical device. It should be prevent in any case blocking biosignal analysis.
Or doesn't it matter?

[tbscope]

You might want to have an event loop in your thread.

It should be prevent in any case blocking biosignal analysis

And yet you use blocking functions :-)

It doesn't really matter. In general, do not use threads for your connections. Do use them if you need to perform long tasks in parallel (send or receive a lot of data is not one of those tasks as it is received in packets).
And if you don't use threads, don't use the blocking functions at all. Don't use them in threads either. The blocking functions are there for a few special cases where the client or server doesn't allow you to communicate asynchronously.

[Suncell]

^^ yeah I should remove them.

But now - I'm still stuck. The readData() function is never called. Maybe deriving the Class CTcpSocket from QObject() is wrong?

Now, server code looks like that:

Server:

MultiServer server;
if (!server.listen(QHostAddress::Any, 15000)) {
   close();
   return;
 }

MultiServer server;
if (!server.listen(QHostAddress::Any, 15000)) {
   close();
   return;
 }

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MultiServer.cpp

MultiServer::MultiServer(QObject *parent)
: QTcpServer(parent)
{
 
}
 
void MultiServer::incomingConnection(int socketDescriptor)
{
    QString msg = "Message from server";
    ConnectionThread *thread = new ConnectionThread(socketDescriptor, msg, this);
    thread->start();
}

MultiServer::MultiServer(QObject *parent)
: QTcpServer(parent)
{

}

void MultiServer::incomingConnection(int socketDescriptor)
{
    QString msg = "Message from server";
    ConnectionThread *thread = new ConnectionThread(socketDescriptor, msg, this);
    thread->start();
}

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ConnectionThread.cpp

ConnectionThread::ConnectionThread(int socketDescriptor, const QString &msg, QObject *parent)
: QThread(parent)
, socketDescriptor(socketDescriptor)
, text(msg)
{
 
}
 
void ConnectionThread::run()
{
	my_sock = new CTcpSocket(socketDescriptor);
 
	my_sock->writeData(text);
 
	while(1)
	{
 
	}
}

ConnectionThread::ConnectionThread(int socketDescriptor, const QString &msg, QObject *parent)
: QThread(parent)
, socketDescriptor(socketDescriptor)
, text(msg)
{

}

void ConnectionThread::run()
{
	my_sock = new CTcpSocket(socketDescriptor);

	my_sock->writeData(text);

	while(1)
	{

	}
}

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tcpsocket.cpp

CTcpSocket::CTcpSocket(int socketDescriptor, QObject *parent)
: QObject(parent)
, m_socketDescriptor(socketDescriptor)
{
	m_tcpSocket = new QTcpSocket();
 
	if (!m_tcpSocket->setSocketDescriptor(m_socketDescriptor)) {
		qDebug() << m_tcpSocket->error();
		return;
	}
 
	connect(m_tcpSocket, SIGNAL(readyRead()), SLOT(readData()));
}
 
 
void CTcpSocket::readData()
{
	//ToDo Implement reading Data
	qDebug() << "try to read";
}
 
 
void CTcpSocket::writeData(QString txt)
{
	qDebug() << "try to write";
 
    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_4_0);
    out << (quint16)0;
    out << txt;
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));
 
    m_tcpSocket->write(block);
}

CTcpSocket::CTcpSocket(int socketDescriptor, QObject *parent)
: QObject(parent)
, m_socketDescriptor(socketDescriptor)
{
	m_tcpSocket = new QTcpSocket();

	if (!m_tcpSocket->setSocketDescriptor(m_socketDescriptor)) {
		qDebug() << m_tcpSocket->error();
		return;
	}

	connect(m_tcpSocket, SIGNAL(readyRead()), SLOT(readData()));
}


void CTcpSocket::readData()
{
	//ToDo Implement reading Data
	qDebug() << "try to read";
}


void CTcpSocket::writeData(QString txt)
{
	qDebug() << "try to write";

    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_4_0);
    out << (quint16)0;
    out << txt;
    out.device()->seek(0);
    out << (quint16)(block.size() - sizeof(quint16));

    m_tcpSocket->write(block);
}

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