[网络协议]Qt实现TCP客户端和服务器通讯程序

复习的心态过一遍之前基础的一些东西，Qt封装了QTcpServer和QTcpSocket两个类，其中QTcpServer继承自QObject，通过listen()函数监听传入的客户端连接，当Client连接上时，QTcpServer会发出newConnection的信号，在对应的槽函数中使用nextPendingConnection()拿到连接的客户端的句柄和信息。

而QTcpSocket则是读写数据的时候使用，过程很简单。

服务器流程：listen->newConnection->nextPendingConnection->readAll/write

客户端流程：connectToHost->waitForConnected->write/readAll

需要注意的是在使用网络相关的类前，需要在pro文件加上QT += network

通信时：

客户端掉线时：

?

QTcpServer服务器代码（包含.h和.cpp）:

.h
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QTcpServer>
#include <QTcpSocket>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

protected slots:
    void onSendBtnClicked();
    void onNewClientConnected();
    void onRecvData();
    void onClientDisconnected();

private:
    void Init();

private:
    Ui::Widget *ui;

private:
    QTcpServer *_tcpServer;
    QTcpSocket *_tcpSocket;
};
#endif // WIDGET_H

.cpp
#include "widget.h"
#include "ui_widget.h"
#include <QHostAddress>
#include <QDebug>

#define MyTcpPort 8886

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

    connect(this->ui->btn_send,&QPushButton::clicked,this,&Widget::onSendBtnClicked);

    Init();

    setWindowTitle("服务端");
}

Widget::~Widget()
{
    delete ui;

    if(_tcpSocket)
    {
        _tcpSocket->disconnect();
        _tcpSocket->abort();
        _tcpSocket->close();
        _tcpSocket->deleteLater();
    }
    if(_tcpServer)
    {
        _tcpServer->close();
        delete _tcpServer;
    }
}

void Widget::Init()
{
    _tcpSocket = new QTcpSocket;
    _tcpServer = new QTcpServer;

    int ret = _tcpServer->listen(QHostAddress::AnyIPv4,MyTcpPort);
    if(ret==0)
    {
        qDebug()<<"_tcpServer->listen is failied";
        return;
    }
    connect(_tcpServer,&QTcpServer::newConnection,this,&Widget::onNewClientConnected);
}

void Widget::onSendBtnClicked()
{
    if(!_tcpSocket) return;

    QString inputText = ui->inputEdit->text();
    if(inputText.isEmpty())
        return;
    //发送数据
    int ret = _tcpSocket->write(inputText.toStdString().c_str());
    if(ret<0)
    {
        qDebug()<<"write to client is failed!";
    }
}

void Widget::onNewClientConnected()
{
    if(_tcpServer->hasPendingConnections())
    {
        _tcpSocket = _tcpServer->nextPendingConnection();
        if(!_tcpSocket->isValid()) return;
        connect(_tcpSocket,&QTcpSocket::readyRead,this,
                &Widget::onRecvData);
        connect(_tcpSocket,&QTcpSocket::disconnected,this,
                &Widget::onClientDisconnected);
    }
}

void Widget::onRecvData()
{
    if(!_tcpSocket) return;
    QString recvData=_tcpSocket->readAll();
    qDebug()<<"recvData:"<<recvData;

    this->ui->recvEdit->append(recvData);
}

void Widget::onClientDisconnected()
{
    QString clientIp = _tcpSocket->peerAddress().toString();
    this->ui->recvEdit->append(clientIp+" is Drop line!");
}

QTcpClient客户端代码（包含.h和.cpp）:

/.h
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QTcpSocket>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    void Init();

protected slots:
    void onSendBtnClicked();
    void onRecvData();

private:
    Ui::Widget *ui;

private:
    QTcpSocket *_tcpClient;
};
#endif // WIDGET_H

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

#define MyTcpPort 8886

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

    connect(this->ui->btn_send,&QPushButton::clicked,this,&Widget::onSendBtnClicked);

    Init();

     setWindowTitle("客户端");
}

Widget::~Widget()
{
    delete ui;

    if(_tcpClient)
    {
        _tcpClient->close();
        _tcpClient->deleteLater();
    }
}

void Widget::Init()
{
    _tcpClient=new QTcpSocket;
    _tcpClient->abort();
    _tcpClient->connectToHost("127.0.0.1",MyTcpPort);
    if(!_tcpClient->waitForConnected(2000))
    {
        qDebug()<<"connect is failed!";
        return;
    }
    qDebug()<<"connect is successful";
    connect(_tcpClient,&QTcpSocket::readyRead,this,&Widget::onRecvData);
}

void Widget::onSendBtnClicked()
{
    if(!_tcpClient) return;

    QString wStr=ui->inputEdit->text();

    int ret = _tcpClient->write(wStr.toStdString().c_str());
    if(ret<0)
    {
        qDebug()<<"send data is failed";
    }
    qDebug()<<"send data is successful!";
}

void Widget::onRecvData()
{
    if(!_tcpClient) return;

    QString recvData= _tcpClient->readAll();
    ui->recvEdit->append(recvData);
    qDebug()<<"recvData:"<<recvData;
}