QTcpSocket communication in a thread

Question

I'm making two application : one is the server and one is the client. The server use QTcpServer and QThread to listen to client. The client use QThread to make a connection to server. The server and the client successfully connected, but the problem is how to communicate data between them. On server side, I put a line to send a data to client using socket->write("hello") when a new client is connected, but the client didn't receive it. The "didn't receive" conjecture based on nothing written on calling QDebug on client side. Also, I want to ask about how to make the client thread always ready to receive data from server but sometimes can be used to send data to server when a PushButton is used. Any help will be appreciated.

client side main.cpp (using a widget)

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include "tcpthread.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_clicked()
{
    TcpThread *tcpThread = new TcpThread(this);
    connect(tcpThread, SIGNAL(finished()), tcpThread, SLOT(deleteLater()));
    tcpThread->start();
}

client side tcpthread.h

#ifndef TCPTHREAD_H
#define TCPTHREAD_H

#include <QThread>
#include <QTcpSocket>

class TcpThread : public QThread
{
    Q_OBJECT
public:
    explicit TcpThread(QObject *parent = 0);
    void run();
signals:
    void error(QTcpSocket::SocketError socketError);
public slots:
    void readyRead();
    void disconnected();
private:
    void processMessage(QByteArray message);
    QTcpSocket *socket;
    qintptr socketDescriptor;
    QByteArray data;
};

#endif // TCPTHREAD_H

client side tcpthread.cpp

#include "tcpthread.h"

TcpThread::TcpThread(QObject *parent) :
    QThread(parent)
{
}

void TcpThread::run()
{
    qDebug() << "Thread started";
    socket = new QTcpSocket();
    connect(socket, SIGNAL(readyRead()), this, SLOT(readyRead()), Qt::DirectConnection);
    connect(socket, SIGNAL(disconnected()), this, SLOT(disconnected()));
    socket->connectToHost("127.0.0.1",1234);
    exec();
}

void TcpThread::readyRead()
{
    data = socket->readAll();
    while(!data.contains('\n'))
    {
        socket->waitForReadyRead();
        data += socket->readAll();
    }
    int bytes = data.indexOf('\n')+1;
    QByteArray message = data.left(bytes);
    data = data.mid(bytes);
    qDebug() << socketDescriptor << " : " << message;
    processMessage(message);
}

void TcpThread::disconnected()
{
    qDebug() << socketDescriptor << " disconnected";
    socket->deleteLater();
    exit(0);
}

void TcpThread::processMessage(QByteArray message)
{
    qDebug() << message << " processed";
}

server side main.cpp

#include "tcpserver.h"
#include <QCoreApplication>

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

    TcpServer tcpServer;
    tcpServer.startServer();

    return a.exec();
}

server side tcpthread.h

#ifndef TCPTHREAD_H
#define TCPTHREAD_H

#include <QThread>
#include <QTcpSocket>
#include <QDebug>

class TcpThread : public QThread
{
    Q_OBJECT
public:
    explicit TcpThread(qintptr ID, QObject *parent = 0);
    void run();
signals:
    void error(QTcpSocket::SocketError socketError);
public slots:
    void readyRead();
    void disconnected();
private:
    void processMessage(QByteArray message);
    QTcpSocket *socket;
    qintptr socketDescriptor;
    QByteArray data;
};

#endif // TCPTHREAD_H

server side tcpthread.cpp #include "tcpthread.h"

TcpThread::TcpThread(qintptr ID, QObject *parent) :
    QThread(parent)
{
    this->socketDescriptor = ID;
}

void TcpThread::run()
{
    qDebug() << "Thread started";
    socket = new QTcpSocket();
    if(!socket->setSocketDescriptor(this->socketDescriptor))
    {
        emit error(socket->error());
        return;
    }
    connect(socket, SIGNAL(readyRead()), this, SLOT(readyRead()), Qt::DirectConnection);
    connect(socket, SIGNAL(disconnected()), this, SLOT(disconnected()));
    qDebug() << socketDescriptor << " connected";
    socket->write("hello");
    exec();
}

void TcpThread::readyRead()
{
    data = socket->readAll();
    while(!data.contains('\n'))
    {
        socket->waitForReadyRead();
        data += socket->readAll();
    }
    int bytes = data.indexOf('\n')+1;
    QByteArray message = data.left(bytes);
    data = data.mid(bytes);
    qDebug() << socketDescriptor << " : " << message;
    processMessage(message);
    //socket->write(data);
}

void TcpThread::disconnected()
{
    qDebug() << socketDescriptor << " disconnected";
    socket->deleteLater();
    exit(0);
}

void TcpThread::processMessage(QByteArray message)
{
    qDebug() << message << " processed";
}