chatmain.h

#ifndef CHATMAIN_H
#define CHATMAIN_H

#include <QMainWindow>
#include <QWidget>
#include <QTcpSocket>
#include <QTcpServer>
#include <QMessageBox>
#include "chatwindow.h"

QT_BEGIN_NAMESPACE
namespace Ui {
class ChatMain;
}
QT_END_NAMESPACE

class ChatMain : public QMainWindow
{
    Q_OBJECT

public:
    ChatMain(QWidget *parent = nullptr);
    ~ChatMain();

private slots:
    void connectToServer();
    void newConnectionSlot(QTcpSocket *socket, QWidget *parent);
    void broadcastMessage(const QString &message);
    void clientDisconnected(QTcpSocket* socket);

private:
    Ui::ChatMain *ui;
    ChatWindow* chatwindow;
    QTcpServer* server;
    QTcpSocket* socket;
    QList<ChatWindow*> clients;
    int cnt = 0;
};
#endif // CHATMAIN_H

chatmain.cpp

#include "chatmain.h"
#include "ui_chatmain.h"
#include "chatwindow.h"

ChatMain::ChatMain(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::ChatMain)
{
    QMainWindow mainWindow;
    ui->setupUi(this);
    setWindowTitle("Chatting Client");
    ui->ipLineEdit->setText("192.168.219.104");

    server = new QTcpServer(this);
    connect(ui->connectBtn, SIGNAL(clicked()), this, SLOT(connectToServer()));

}

ChatMain::~ChatMain()
{
    delete ui;
    delete socket;
}


void ChatMain::connectToServer()
{
    cnt++; // connect횟수
    QString host = ui->ipLineEdit->text(); // 서버주소
    bool ok;
    qint16 port = ui->portLineEdit->text().toInt(&ok);// 포트번호
    QString ports = QString::number(port);
    if (host.isEmpty()) {
        QMessageBox::critical(nullptr, "Error", "서버 주소를 입력하세요.");
        return;
    }
    if(!ok) {
        QMessageBox::critical(nullptr, "Error", "유효한 포트 번호를 입력하세요.");
        return;
    }

    if(server->listen(QHostAddress(host), port)) {
        ui->connectBtn->setText("연결 끊기");

    } else {
        ui->connect_state->append("Connection failed!");
        return;
    }


    ui->connect_state->append("Connected to server!");

    chatwindow = new ChatWindow(socket, this);
    chatwindow->show();

    connect(server, SIGNAL(newConnection()), this, SLOT(newConnectionSlot(socket, this)));

}

void ChatMain::newConnectionSlot(QTcpSocket *socket, QWidget *parent) {


    chatwindow = new ChatWindow(socket, parent);
    chatwindow->show();


    ChatWindow *client = new ChatWindow(socket, this);

    clients.append(client);

    connect(client, SIGNAL(disconnected()), this, SLOT(clientDisconnected(socket)));


    client -> sendMessage("USERNAME");

    // 클라이언트에게 사용자 이름 설정 요청 메세지 전송
    connect(client, SIGNAL(messageReceived(QString)), this, SLOT(broadcastMessage("USERNAME")));

}

void ChatMain::broadcastMessage(const QString &message) {
    for (ChatWindow *client : clients) {
        client->sendMessage(message);
    }
}

void ChatMain::clientDisconnected(QTcpSocket* socket) {
    // 연결 종료 시 처리 내용 작성
    clients.removeOne((void*)socket);
    socket->deleteLater();
}

chatwindow.h

#ifndef CHATWINDOW_H
#define CHATWINDOW_H

#include <QMainWindow>
#include <QObject>
#include <QTcpSocket>

namespace Ui {
class ChatWindow;
}

class ChatWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit ChatWindow(QTcpSocket *socket, QWidget *parent = 0);
    ~ChatWindow();

signals:
    void disconnected();
    void messageReceived(QString);

private:
    Ui::ChatWindow *ui;
    QTcpSocket *socket;
    QString username;

public slots:
    void readMessage();
    void sendMessage(const QString &message);
    void setUserName();

};


#endif // CHATWINDOW_H

chatwindow.cpp

#include "chatwindow.h"
#include "ui_chatwindow.h"

ChatWindow::ChatWindow(QTcpSocket *socket, QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::ChatWindow)
    , socket(socket)
{
    ui->setupUi(this);
    connect(ui->setUserName, SIGNAL(clicked()), this, SLOT(setUserName()));
    connect(parent, SIGNAL(&QTcpSocket::readyRead), this, SLOT(readMessage()));
    connect(parent, SIGNAL(&QTcpSocket::disconnected), this, SLOT(disconnected()));
}


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

void ChatWindow::setUserName() {
    username = ui->userName->text();

}


void ChatWindow::readMessage() {
    QByteArray data = socket->readAll();
    QString message(data);

    // 메시지 처리 (예: 사용자 이름 설정, 채팅 메시지 전송 등)
    if (message.startsWith("USERNAME")) {
        // 사용자 이름 설정
        username = ui->userName->text();
        emit messageReceived("[" + username + "] 접속했습니다.");
        ui->connectedUsers->setText("[" + username + "] 접속했습니다.");
    } else {
        // 채팅 메시지 전송
        emit messageReceived("[" + username + "]: " + message);
    }
}

void ChatWindow::sendMessage(const QString &message) {
    socket->write(message.toUtf8());
}

chatmain.ui

chatwindow.ui