Design of Qt TCP network host computer (combined with lower computer through network programming)

Table of contents

TCP protocol basics

QTcpServer and QAbstractSocket main interface functions

TCP application

1. Server

2.Client

The upper computer communicates with the lower computer through network programming

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TCP protocol basics

Transmission Control Protocol (TCP) is a connection-oriented, reliable, byte stream-based transport layer communication protocol

TCP’s congestion control algorithm (also known as AIMD algorithm). The algorithm mainly consists of four main parts: slow start, congestion avoidance, fast retransmission and fast recovery

TCP communication must establish a TCP connection (client and server). Qt provides the QTcpSocket class and QTcpServer class specifically for establishing TCP communication programs. The server uses QTcpServer to listen to the port and establish the server; QTcpSocket is used to establish a connection and use sockets for communication.

QTcpServer and QAbstractSocket Main interface functions

QTcpServer is a class inherited from QOjbect, which is used by the server to establish network monitoring and create network socket connections. The main interface functions of QTcpServer are as follows:

The main interface functions of QAbstractSocket are as follows:

TCP application

1. Server

UI structure:

Code example:

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

#include <QTcpServer> // 专门用于建立TCP连接并传输数据信息
#include <QtNetwork> // 此模块提供开发TCP/IP客户端和服务器的类

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;


    // 自定义如下
private:
    QTcpServer *tcpserver; //TCP服务器
    QTcpSocket *tcpsocket;// TCP通讯socket
    QString GetLocalIpAddress(); // 获取本机的IP地址

private slots:
    void clientconnect();
    void clientdisconnect();
    void socketreaddata();
    void newconnection();


    void on_pushButton_Start_clicked();
    void on_pushButton_Stop_clicked();
    void on_pushButton_Send_clicked();

protected:
    void closeEvent(QCloseEvent *event);

};
#endif // MAINWINDOW_H

main.cpp

#include "mainwindow.h"

#include <QApplication>

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

mainwindow.cpp

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

#include <QMessageBox>

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

    QString strip=GetLocalIpAddress();
    // QMessageBox::information(this,"数据",strip,QMessageBox::Yes);

    ui->comboBoxIp->addItem(strip);


    tcpserver=new QTcpServer(this);

    connect(tcpserver,SIGNAL(newConnection()),this,SLOT(newconnection()));

}

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


void MainWindow::on_pushButton_Start_clicked()
{
    QString ip=ui->comboBoxIp->currentText();
    quint16 port=ui->spinBoxPort->value();

    QHostAddress address(ip);
    tcpserver->listen(address,port);

    ui->plainTextEdit_DispMsg->appendPlainText("$$$$$$$$$$开始监听$$$$$$$$$$");
    ui->plainTextEdit_DispMsg->appendPlainText("$$$$$$$$$$服务器地址$$$$$$$$$$："+
                                               tcpserver->serverAddress().toString());
    ui->plainTextEdit_DispMsg->appendPlainText("$$$$$$$$$$服务器端口$$$$$$$$$$："+
                                               QString::number(tcpserver->serverPort()));
    ui->pushButton_Start->setEnabled(false);
    ui->pushButton_Stop->setEnabled(true);

}

void MainWindow::on_pushButton_Stop_clicked()
{
    if(tcpserver->isListening())
    {
        tcpserver->close();
        ui->pushButton_Start->setEnabled(true);
        ui->pushButton_Stop->setEnabled(false);
    }

}

void MainWindow::on_pushButton_Send_clicked()
{
    QString strmsg=ui->lineEdit_InputMsg->text();
    ui->plainTextEdit_DispMsg->appendPlainText("[out]:"+strmsg);

    ui->lineEdit_InputMsg->clear();

    QByteArray str=strmsg.toUtf8();
    str.append("\n");
    tcpsocket->write(str);
}


QString MainWindow::GetLocalIpAddress() // 获取本机的IP地址
{
    QString hostname=QHostInfo::localHostName();
    QHostInfo hostinfo=QHostInfo::fromName(hostname);

    QString localip="";

    QList<QHostAddress> addresslist=hostinfo.addresses();

    if(!addresslist.isEmpty())
    {
        for (int i=0;i<addresslist.count();i++)
        {
            QHostAddress addrhost=addresslist.at(i);
            if(QAbstractSocket::IPv4Protocol==addrhost.protocol())
            {
                localip=addrhost.toString();
                break;
            }

        }
    }

    return localip;
}

void MainWindow::clientconnect()
{
    // 客户端连接
    ui->plainTextEdit_DispMsg->appendPlainText("**********客户端socket连接**********");
    ui->plainTextEdit_DispMsg->appendPlainText("**********peer address:"+
                                               tcpsocket->peerAddress().toString());
    ui->plainTextEdit_DispMsg->appendPlainText("**********peer port:"+
                                               QString::number(tcpsocket->peerPort()));

}

void MainWindow::clientdisconnect()
{
    // 客户端断开连接
    ui->plainTextEdit_DispMsg->appendPlainText("**********客户端socket断开连接**********");
    tcpsocket->deleteLater();

}

void MainWindow::socketreaddata()
{
    // 读取数据
    while(tcpsocket->canReadLine())
        ui->plainTextEdit_DispMsg->appendPlainText("[in]"+tcpsocket->readLine());

}

void MainWindow::newconnection()
{
    tcpsocket=tcpserver->nextPendingConnection();

    connect(tcpsocket,SIGNAL(connected()),this,SLOT(clientconnect()));
    clientconnect();

    connect(tcpsocket,SIGNAL(disconnected()),this,SLOT(clientdisconnect()));

    connect(tcpsocket,SIGNAL(readyRead()),this,SLOT(socketreaddata()));

    connect(tcpsocket,SIGNAL(stateChanged(QAbstractSocket::SocketState)),
            this,SLOT(OnSocketStateChanged(QAbstractSocket::SocketState)));


}

void MainWindow::closeEvent(QCloseEvent *event)
{
    if(tcpserver->isListening())
        tcpserver->close();

    event->accept();
}

2.Client

UI structure:

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>


#include <QTcpSocket>
#include <QHostAddress>
#include <QHostInfo>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui::MainWindow *ui;


private:
    QTcpSocket *tcpclient; // 客户端tcpclient
    QString getlocalip(); // 获取本机IP地址

protected:
    void closeEvent(QCloseEvent *event);

private slots:
    void connectfunc();
    void disconnectfunc();
    void socketreaddata();





    void on_pushButton_Connect_clicked();
    void on_pushButton_Send_clicked();
    void on_pushButton_Disconnect_clicked();
};
#endif // MAINWINDOW_H

main.cpp

#include "mainwindow.h"

#include <QApplication>

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

mainwindow.cpp

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

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

    tcpclient=new QTcpSocket(this);

    QString strip=getlocalip();

    ui->comboBoxIp->addItem(strip);


    connect(tcpclient,SIGNAL(connected()),this,SLOT(connectfunc()));
    connect(tcpclient,SIGNAL(disconnected()),this,SLOT(disconnectfunc()));
    connect(tcpclient,SIGNAL(readyRead()),this,SLOT(socketreaddata()));


}

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


void MainWindow::on_pushButton_Connect_clicked()
{
    QString addr=ui->comboBoxIp->currentText();
    quint16 port=ui->spinBoxPort->value();
    tcpclient->connectToHost(addr,port);
}

void MainWindow::on_pushButton_Send_clicked()
{
    QString strmsg=ui->lineEdit_InputMsg->text();
    ui->plainTextEdit_DispMsg->appendPlainText("[out]:"+strmsg);
    ui->lineEdit_InputMsg->clear();

    QByteArray str=strmsg.toUtf8();
    str.append('\n');
    tcpclient->write(str);

}


void MainWindow::on_pushButton_Disconnect_clicked()
{
    if(tcpclient->state()==QAbstractSocket::ConnectedState)
        tcpclient->disconnectFromHost();
}




QString MainWindow::getlocalip() // 获取本机IP地址
{
    QString hostname=QHostInfo::localHostName();
    QHostInfo hostinfo=QHostInfo::fromName(hostname);

    QString localip="";

    QList<QHostAddress> addlist=hostinfo.addresses();
    if(!addlist.isEmpty())
    {
        for (int i=0;i<addlist.count();i++)
        {
            QHostAddress ahost=addlist.at(i);
            if(QAbstractSocket::IPv4Protocol==ahost.protocol())
            {
                localip=ahost.toString();
                break;
            }
        }
    }

    return localip;
}


void MainWindow::closeEvent(QCloseEvent *event)
{
    if(tcpclient->state()==QAbstractSocket::ConnectedState)
    {
        tcpclient->disconnectFromHost();
    }
    event->accept();

}


void MainWindow::connectfunc()
{
    ui->plainTextEdit_DispMsg->appendPlainText("**********已经连接到服务器端**********");
    ui->plainTextEdit_DispMsg->appendPlainText("**********peer address:"+
                                               tcpclient->peerAddress().toString());
    ui->plainTextEdit_DispMsg->appendPlainText("**********peer port:"+
                                               QString::number(tcpclient->peerPort()));

    ui->pushButton_Connect->setEnabled(false);
    ui->pushButton_Disconnect->setEnabled(true);

}
void MainWindow::disconnectfunc()
{
    ui->plainTextEdit_DispMsg->appendPlainText("**********已断开与服务器端的连接**********");

    ui->pushButton_Connect->setEnabled(true);
    ui->pushButton_Disconnect->setEnabled(false);

}
void MainWindow::socketreaddata()
{
    while(tcpclient->canReadLine())
        ui->plainTextEdit_DispMsg->appendPlainText("[in]:"+tcpclient->readLine());

}

The upper computer communicates with the lower computer through network programming

Qt as the host computer

51, 32 microcontroller or ARM development board is opened as the slave computer

Communication through network programming

The upper computer can be used as a server or client, and the lower computer can also be used as a server or client, which can be implemented according to the respective project requirements.