chat_QT服务器端：

//.h
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include<QTcpServer>    //服务器类
#include<QTcpSocket>    //客户端类
#include<QMessageBox>   //对话框类
#include<QList>     //链表容器
#include<QDebug>    //信息调试类

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

private slots:
    void on_pushButton_clicked();
    void newConnection_slot();
    void readyRead_muslot();

private:
    Ui::Widget *ui;

    //定义服务器指针
    QTcpServer *server;

    //定义客户端容器
    QList<QTcpSocket *>socketList;

};
#endif // WIDGET_H

//.cpp
#include "widget.h"
#include "ui_widget.h"

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

    //给服务器指针实例化空间
    server = new QTcpServer(this);
}

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


void Widget::on_pushButton_clicked()
{
    //获取ui界面上的端口号
    quint16 port = ui->lineEdit->text().toUInt();

    //将服务器设置监听状态
    if(server->listen(QHostAddress::Any, port)){
        QMessageBox::information(this, "提示", "客户端连接成功");
    }else{
        QMessageBox::information(this, "提示", "客户端连接失败");
    }

    //将客户端想要连接时服务器发射的newConnect信号与对应槽函数连接
    connect(server, &QTcpServer::newConnection, this, &Widget::newConnection_slot);

}

//处理newCOnnection信号对应的槽函数
void Widget::newConnection_slot(){
    //获取最新连接的客户端套接字
    QTcpSocket *s = server->nextPendingConnection();

    //将套接字放入客户端容器中
    socketList.push_back(s);

    //将readyRead信号与对应的槽函数连接
    connect(s, &QTcpSocket::readyRead, this, &Widget::readyRead_muslot);

}

void Widget::readyRead_muslot(){
    //移除无效的客户端
    for(int i = 0; i < socketList.count(); i++){
        //查看客户端状态
        if(socketList.at(i) == 0){
            socketList.removeAt(i);
        }
    }

    //遍历客户端套接字，查看那个客户端有数据
    for(int i = 0; i < socketList.count(); i++){
        //判断套接字中是否有数据
        QByteArray msg = socketList.at(i)->readAll();

        //将数据显示到ui界面上
        ui->listWidget->addItem(QString::fromLocal8Bit(msg));

        //将数据发射给所有的客户端套接字中
        for(int j = 0; j < socketList.count(); j++){
            socketList.at(j)->write(msg);
        }

    }

}

思维导图：