Клиент
#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->connect(&m_client, SIGNAL(readyRead()), SLOT(readyRead()));
 
    m_client.connectToHost("127.0.0.1", 7777);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::readyRead()
{
    QByteArray data = m_client.readAll();
 
    ui->plainTextEdit->appendPlainText(QString(data));
}
 
void MainWindow::on_pushButton_clicked()
{
// ...........
}
Сервер

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QProcess>
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    m_server.listen(QHostAddress::Any, 7777);
 
    this->connect(&m_server, SIGNAL(newConnection()), SLOT(NewConnection()));
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::NewConnection()
{
    QPointer<QTcpSocket> client(m_server.nextPendingConnection());
 
    this->connect(client.data(), SIGNAL(readyRead()), SLOT(readyRead()));
 
    m_clients.append(client);
 
    ui->plainTextEdit->appendPlainText("NewConnection");
}
 
void  MainWindow::readyRead()
{
//.........
}