【Qt】modbus之TCP模式写操作

00. 目录

01. 概述

Qt中几个常用的串口modbus类

QModbusRtuSerialSlave       //modbus串口通信方式下的服务器类
QModbusRtuSerialMaster      //串口通信方式下的客户端类
QModbusServer               // QModbusServer类接收和处理modbus的请求。
QModbusDataUnit             //存储接收和发送数据的类，数据类型为1bit和16bit
QModbusReply                //客户端访问服务器后得到的回复（如客户端读服务器数据时包含数据信息）

02. 开发环境

Windows系统：Windows10

Qt版本：Qt5.15或者Qt6

Pro配置文件如下

QT       += core gui serialbus serialport

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \\
    main.cpp \\
    widget.cpp

HEADERS += \\
    widget.h

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

03. 读Coils程序示例

widget.h文件

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

//前向声明
class QModbusClient;
class QModbusReply;


QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    Ui::Widget *ui;

    QModbusClient *modbusDevice = nullptr;


private slots:
    void onReadReady();
    void onModbusStateChanged(int state);
    void on_btnConnect_clicked();
    void on_btnCoil_clicked();
    void on_btnDiscreteInputs_clicked();
    void on_btnInputRegisters_clicked();
    void on_btnHoldingRegisters_clicked();
    void on_btnCoil_2_clicked();
    void on_btnHoldingRegisters_2_clicked();
};
#endif // WIDGET_H

widget.cpp文件

#include "widget.h"
#include "ui_widget.h"
#include <QDebug>
#include <QModbusTcpClient>


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

    //1. 创建QModbusDevice对象
    modbusDevice = new QModbusTcpClient(this);

    //禁用所有的读操作
    ui->btnCoil->setEnabled(false);
    ui->btnDiscreteInputs->setEnabled(false);
    ui->btnHoldingRegisters->setEnabled(false);
    ui->btnInputRegisters->setEnabled(false);

    //禁用所有的写操作
    ui->btnCoil_2->setEnabled(false);
    ui->btnHoldingRegisters_2->setEnabled(false);

    connect(modbusDevice, &QModbusClient::errorOccurred, [this](QModbusDevice::Error) {
        qDebug() << "new Error: " << modbusDevice->errorString();
    });

    if (nullptr == modbusDevice)
    {
        qDebug() << "Cannot Create Modbus Client";
    }
    else
    {
        connect(modbusDevice, &QModbusClient::stateChanged,
                this, &Widget::onModbusStateChanged);
    }


}

//析构函数
Widget::~Widget()
{
    if (modbusDevice)
    {
        modbusDevice->disconnectDevice();
    }

    delete modbusDevice;

    delete ui;
}


void Widget::onReadReady()
{
    auto reply = qobject_cast<QModbusReply*>(sender());
    if (nullptr == reply)
    {
        return;
    }

    //判断是否出错
    if (reply->error() == QModbusDevice::NoError)
    {
        //读取响应数据
        const QModbusDataUnit responseData = reply->result();

        qDebug() << "读到数据为：" << responseData.values();

    }
    else if (reply->error() == QModbusDevice::ProtocolError)
    {
        qDebug() << "Read response Protocol error: " << reply->errorString();
    }
    else
    {
        qDebug() << "Read response Error: " << reply->errorString();
    }


    //删除reply
    reply->deleteLater();
}


void Widget::onModbusStateChanged(int state)
{
    //判断Modbus设备连接是否处于连接状态
    if (state == QModbusDevice::UnconnectedState)
    {
        qDebug() << "TCP Client连接到Server 未连接";
        ui->btnConnect->setText(tr("连接"));

        ui->btnCoil->setEnabled(false);
        ui->btnDiscreteInputs->setEnabled(false);
        ui->btnHoldingRegisters->setEnabled(false);
        ui->btnInputRegisters->setEnabled(false);

        ui->btnCoil_2->setEnabled(false);
        ui->btnHoldingRegisters_2->setEnabled(false);

    }
    else if (state == QModbusDevice::ConnectingState)
    {
        qDebug() << "TCP Client正在连接Server";
    }
    else if (state == QModbusDevice::ConnectedState)
    {
        qDebug() << "TCP Client已经连接到Server";
        ui->btnConnect->setText(tr("断开连接"));

        ui->btnCoil->setEnabled(true);
        ui->btnDiscreteInputs->setEnabled(true);
        ui->btnHoldingRegisters->setEnabled(true);
        ui->btnInputRegisters->setEnabled(true);

        ui->btnCoil_2->setEnabled(true);
        ui->btnHoldingRegisters_2->setEnabled(true);


    }
    else if (state == QModbusDevice::ClosingState)
    {
        qDebug() << "设备已经被关闭";
    }
}

//连接按钮槽函数
void Widget::on_btnConnect_clicked()
{
    if (!modbusDevice)
    {
        return;
    }

    if (modbusDevice->state() != QModbusDevice::ConnectedState)
    {
        modbusDevice->setConnectionParameter(QModbusDevice::NetworkAddressParameter, "127.0.0.1");
        modbusDevice->setConnectionParameter(QModbusDevice::NetworkPortParameter, 10086);

        //设置超时时间
        modbusDevice->setTimeout(1000); //1秒
        //设置失败重试次数
        modbusDevice->setNumberOfRetries(3);

        //连接到服务端
        bool ok = modbusDevice->connectDevice();
        if (!ok)
        {
            qDebug() << "modbusDevice->connectDevice failed";
        }
    }
    else
    {
        //断开连接
        modbusDevice->disconnectDevice();
        ui->btnConnect->setText(tr("连接"));

        ui->btnCoil->setEnabled(false);
        ui->btnDiscreteInputs->setEnabled(false);
        ui->btnHoldingRegisters->setEnabled(false);
        ui->btnInputRegisters->setEnabled(false);
        ui->btnCoil_2->setEnabled(false);
        ui->btnHoldingRegisters_2->setEnabled(false);
    }

}

//读线圈
void Widget::on_btnCoil_clicked()
{
    //QModbusDataUnit::Coils 从地址0开始读取10个线圈值
    QModbusDataUnit data(QModbusDataUnit::Coils, 0, 10);

    auto reply = modbusDevice->sendReadRequest(data, 0x1);
    if (nullptr == reply)
    {
        qDebug() << "发送请求数据失败: " << modbusDevice->errorString();
    }
    else
    {
        if (!reply->isFinished())
        {
            connect(reply, &QModbusReply::finished, this, &Widget::onReadReady);
        }
        else
        {
            //broadcast replies return immediately
            delete reply;
        }
    }
}

//读离散输入
void Widget::on_btnDiscreteInputs_clicked()
{
    //QModbusDataUnit::DiscreteInputs 从地址0开始读取10个离散输入值
    QModbusDataUnit data(QModbusDataUnit::DiscreteInputs, 0, 10);

    auto reply = modbusDevice->sendReadRequest(data, 0x1);
    if (nullptr == reply)
    {
        qDebug() << "发送请求数据失败: " << modbusDevice->errorString();
    }
    else
    {
        if (!reply->isFinished())
        {
            connect(reply, &QModbusReply::finished, this, &Widget::onReadReady);
        }
        else
        {
            //broadcast replies return immediately
            delete reply;
        }
    }
}

//读输入寄存器
void Widget::on_btnInputRegisters_clicked()
{
    //QModbusDataUnit::InputRegisters 从地址0开始读取10个输入寄存器的值
    QModbusDataUnit data(QModbusDataUnit::InputRegisters, 0, 10);

    auto reply = modbusDevice->sendReadRequest(data, 0x1);
    if (nullptr == reply)
    {
        qDebug() << "发送请求数据失败: " << modbusDevice->errorString();
    }
    else
    {
        if (!reply->isFinished())
        {
            connect(reply, &QModbusReply::finished, this, &Widget::onReadReady);
        }
        else
        {
            //broadcast replies return immediately
            delete reply;
        }
    }
}

//读保持寄存器
void Widget::on_btnHoldingRegisters_clicked()
{
    //从地址0开始读取10个保持寄存器的值
    QModbusDataUnit data(QModbusDataUnit::HoldingRegisters, 0, 10);

    auto reply = modbusDevice->sendReadRequest(data, 0x1);
    if (nullptr == reply)
    {
        qDebug() << "发送请求数据失败: " << modbusDevice->errorString();
    }
    else
    {
        if (!reply->isFinished())
        {
            connect(reply, &QModbusReply::finished, this, &Widget::onReadReady);
        }
        else
        {
            //broadcast replies return immediately
            delete reply;
        }
    }
}

//写线圈
void Widget::on_btnCoil_2_clicked()
{
    //从地址0开始写10个线圈的值
    QModbusDataUnit writeData(QModbusDataUnit::Coils, 0, 10);
    for (int i = 0; i < writeData.valueCount(); i++)
    {
        writeData.setValue(i, (i * i) % 2);
    }

    qDebug() << "发送的数据为： " << writeData.values();

    QModbusReply* reply = modbusDevice->sendWriteRequest(writeData, 1);
    if (reply)
    {
        if (!reply->isFinished())
        {
            //接收响应信息
            connect(reply, &QModbusReply::finished, this, [this, reply](){
                if (reply->error() == QModbusDevice::ProtocolError)
                {
                    //接收到的响应信息是协议错误
                    qDebug() << "写入数据错误：" << reply->errorString();
                }
                else if (reply->error() != QModbusDevice::NoError)
                {
                    //接收到的响应消息是其它错误
                    qDebug() << "写入数据错误： " << reply->errorString();
                }
                else
                {
                    //接收到的消息没有错误 一般没有必要解析响应消息
                    const QModbusDataUnit data = reply->result();

                    qDebug() << "消息数据个数：" << data.valueCount() << " :" << data.values();

                }

                reply->deleteLater();
            });
        }
        else
        {
            //发送没有响应数据
            //broadcast replies return immediately
            reply->deleteLater();
        }
    }
    else
    {
        qDebug() << "sendWriteRequest Error: " << reply->errorString();
    }
}


//写保持寄存器
void Widget::on_btnHoldingRegisters_2_clicked()
{


}

执行结果

16:02:56: Starting D:\\ProgramData\\Qt\\build-Test1-Desktop_Qt_5_15_2_MinGW_32_bit-Debug\\debug\\Test1.exe ...
TCP Client正在连接Server
TCP Client已经连接到Server
发送的数据为：  QVector(0, 1, 0, 1, 0, 1, 0, 1, 0, 1)
消息数据个数： 10  : QVector(0, 1, 0, 1, 0, 1, 0, 1, 0, 1)
设备已经被关闭
TCP Client连接到Server 未连接
16:03:17: D:\\ProgramData\\Qt\\build-Test1-Desktop_Qt_5_15_2_MinGW_32_bit-Debug\\debug\\Test1.exe exited with code 0

04. 读HoldingRegisters程序示例

widget.h文件

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

//前向声明
class QModbusClient;
class QModbusReply;


QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    Ui::Widget *ui;

    QModbusClient *modbusDevice = nullptr;


private slots:
    void onReadReady();
    void onModbusStateChanged(int state);
    void on_btnConnect_clicked();
    void on_btnCoil_clicked();
    void on_btnDiscreteInputs_clicked();
    void on_btnInputRegisters_clicked();
    void on_btnHoldingRegisters_clicked();
    void on_btnCoil_2_clicked();
    void on_btnHoldingRegisters_2_clicked();
};
#endif // WIDGET_H

widget.cpp文件

//写保持寄存器
void Widget::on_btnHoldingRegisters_2_clicked()
{
    QModbusDataUnit writeData(QModbusDataUnit::HoldingRegisters, 0, 10);
    for (int i = 0; i < writeData.valueCount(); i++)
    {
        writeData.setValue(i, i * i);
    }

    qDebug() << "发送的数据为： " << writeData.values();

    QModbusReply* reply = modbusDevice->sendWriteRequest(writeData, 1);
    if (reply)
    {
        if (!reply->isFinished())
        {
            //接收响应信息
            connect(reply, &QModbusReply::finished, this, [this, reply](){
                if (reply->error() == QModbusDevice::ProtocolError)
                {
                    //接收到的响应信息是协议错误
                    qDebug() << "写入数据错误：" << reply->errorString();
                }
                else if (reply->error() != QModbusDevice::NoError)
                {
                    //接收到的响应消息是其它错误
                    qDebug() << "写入数据错误： " << reply->errorString();
                }
                else
                {
                    //接收到的消息没有错误 一般没有必要解析响应消息
                    const QModbusDataUnit data = reply->result();

                    qDebug() << "消息数据个数：" << data.valueCount() << " :" << data.values();

                }

                reply->deleteLater();
            });
        }
        else
        {
            //发送没有响应数据
            //broadcast replies return immediately
            reply->deleteLater();
        }
    }
    else
    {
        qDebug() << "sendWriteRequest Error: " << reply->errorString();
    }
}

执行结果

16:07:56: Starting D:\\ProgramData\\Qt\\build-Test1-Desktop_Qt_5_15_2_MinGW_32_bit-Debug\\debug\\Test1.exe ...
TCP Client正在连接Server
TCP Client已经连接到Server
发送的数据为：  QVector(0, 1, 4, 9, 16, 25, 36, 49, 64, 81)
消息数据个数： 10  : QVector(0, 1, 4, 9, 16, 25, 36, 49, 64, 81)

07. 综合示例

程序界面

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settingdialog.h文件

#ifndef SETTINGDIALOG_H
#define SETTINGDIALOG_H

#include <QDialog>
#include <QtSerialPort>

namespace Ui {
class SettingDialog;
}

//串口设置相关类
class SettingDialog : public QDialog
{
    Q_OBJECT

public:
    struct Settings
    {
        //串口名
        QString serialName = "COM3";
        //校验位
        int parity = QSerialPort::NoParity;
        //波特率
        int baud = QSerialPort::Baud19200;
        //数据位
        int dataBits = QSerialPort::Data8;
        //停止位
        int stopBits = QSerialPort::OneStop;

        //响应时间
        int responseTime = 1000;
        //重试次数
        int numberOfRetries = 3;
    };

    explicit SettingDialog(QWidget *parent = nullptr);
    ~SettingDialog();

    //返回参数设置信息
    Settings  settings() const;

private slots:
    void on_btnApply_clicked();

private:
    Ui::SettingDialog *ui;
    Settings m_settings;
};

#endif // SETTINGDIALOG_H

settingdialog.cpp文件

#include "settingdialog.h"
#include "ui_settingdialog.h"

//构造函数
SettingDialog::SettingDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::SettingDialog)
{
    ui->setupUi(this);

    //设置默认参数信息
    ui->serialNameLineEdit->setText(tr("COM3"));
    ui->parityComboBox->setCurrentIndex(0);

    ui->baudComboBox->setCurrentText(QString::number(m_settings.baud));
    ui->dataBitComboBox->setCurrentText(QString::number(m_settings.dataBits));
    ui->stopBitComboBox->setCurrentText(QString::number(m_settings.stopBits));

    ui->spinBoxTimeOut->setValue(m_settings.responseTime);
    ui->spinBoxRetry->setValue(m_settings.numberOfRetries);

}

//析构函数
SettingDialog::~SettingDialog()
{
    delete ui;
}

//返回参数信息
SettingDialog::Settings SettingDialog::settings() const
{
    return m_settings;
}

//引用按钮槽函数
void SettingDialog::on_btnApply_clicked()
{
    m_settings.serialName = ui->serialNameLineEdit->text();
    m_settings.parity = ui->parityComboBox->currentText().toInt();
    m_settings.baud = ui->baudComboBox->currentText().toInt();
    m_settings.dataBits = ui->dataBitComboBox->currentText().toInt();
    m_settings.stopBits = ui->stopBitComboBox->currentText().toInt();

    m_settings.responseTime = ui->spinBoxTimeOut->value();
    m_settings.numberOfRetries = ui->spinBoxRetry->value();

    //隐藏参数设置对话框
    hide();
}

mainwindow.h文件

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QModbusDataUnit>

QT_BEGIN_NAMESPACE

namespace Ui
{
    class MainWindow;
}

class SettingDialog;
class QModbusClient;
class QModbusReply;


QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

    //信号与槽进行关联
    void initActions();

    //读请求数据包封装
    QModbusDataUnit readRequest() const;

private slots:
    void onConnectButtonClicked();

    void onConnectTypeChanged(int);

    void onModbusStateChanged(int state);

    void onReadButtonClicked();
    void onReadReady();

private:
    Ui::MainWindow *ui = nullptr;

    SettingDialog *m_settingDialog = nullptr;

    QModbusClient *modbusDevice = nullptr;

    QModbusReply *reply = nullptr;

};
#endif // MAINWINDOW_H

mainwindow.cpp文件

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
#include "settingdialog.h"
#include <QModbusRtuSerialMaster>
#include <QModbusReply>
#include <QStandardItemModel>
#include <QModbusDataUnit>
#include <QModbusTcpClient>

//连接类型枚举变量
enum ModbusConnection {
    Serial,
    Tcp
};


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

    //创建对象
    m_settingDialog = new SettingDialog(this);

    //初始化信号与槽
    initActions();

    //创建写模型
    writeModel = new WriteRegisterModel(this);
    writeModel->setStartAddress(ui->sbWriteStartAddr->value());
    writeModel->setNumberOfValues(ui->cbWriteCount->currentText());

    //MVC
    ui->treeViewWrite->setModel(writeModel);
    //隐藏第二列
    ui->treeViewWrite->hideColumn(2);
    connect(writeModel, &WriteRegisterModel::updateViewport,
            ui->treeViewWrite->viewport(), QOverload<>::of(&QWidget::update));


    //默认为串口连接方式
    ui->cbConnType->setCurrentIndex(0);
    onConnectTypeChanged(0);

    auto model = new QStandardItemModel(10, 1, this);
    for (int i = 0; i < 10; i++)
    {
        model->setItem(i, new QStandardItem(QStringLiteral("%1").arg(i + 1)));
    }

    ui->cbWriteCount->setModel(model);
    ui->cbWriteCount->setCurrentText("10");

    connect(ui->cbWriteCount, &QComboBox::currentTextChanged,
            writeModel, &WriteRegisterModel::setNumberOfValues);

    auto valueChanged = QOverload<int>::of(&QSpinBox::valueChanged);
    connect(ui->sbWriteStartAddr, valueChanged, writeModel, &WriteRegisterModel::setStartAddress);


    connect(ui->sbWriteStartAddr, valueChanged, this, [this, model](int i){
        int lastIndex = 0;
        const int curIndex = ui->cbWriteCount->currentIndex();
        for (int j = 0; j < 10; j++)
        {
            //设置使能
            if (j < (10 - i))
            {
                lastIndex = j;
                model->item(j)->setEnabled(true);
            }
            else
            {
                //设置禁用
                model->item(j)->setEnabled(false);
            }
        }

        if (curIndex > lastIndex)
        {
            ui->cbWriteCount->setCurrentIndex(lastIndex);
        }

    });
}


//析构函数
MainWindow::~MainWindow()
{
    if (modbusDevice)
    {
        modbusDevice->disconnectDevice();
        delete modbusDevice;
    }
    delete ui;
}



//信号与槽进行关联s
void MainWindow::initActions()
{
    //使能部分功能
    ui->actionConnect->setEnabled(true);
    ui->actionDisconnect->setEnabled(false);
    ui->actionQuit->setEnabled(true);
    ui->actionOption->setEnabled(true);

    //禁用读写操作
    ui->btnRead->setEnabled(false);
    ui->btnWrite->setEnabled(false);
    ui->btnReadWrite->setEnabled(false);


    //信号与槽关联
    connect(ui->btnConnect, &QPushButton::clicked,
            this, &MainWindow::onConnectButtonClicked);

    connect(ui->actionConnect, &QAction::triggered,
            this, &MainWindow::onConnectButtonClicked);

    connect(ui->actionDisconnect, &QAction::triggered,
            this, &MainWindow::onConnectButtonClicked);

    //读操作按钮槽函数关联
    connect(ui->btnRead, &QPushButton::clicked,
            this, &MainWindow::onReadButtonClicked);

    connect(ui->btnWrite, &QPushButton::clicked,
            this, &MainWindow::onWriteButtonClicked);

    connect(ui->btnReadWrite, &QPushButton::clicked,
            this, &MainWindow::onReadWriteButtonClicked);

    connect(ui->cbRegisterType, QOverload<int>::of(&QComboBox::currentIndexChanged),
            this, &MainWindow::onWriteTableChanged);

    connect(ui->cbConnType, QOverload<int>::of(&QComboBox::currentIndexChanged),
            this, &MainWindow::onConnectTypeChanged);

    //退出菜单
    connect(ui->actionQuit, &QAction::triggered, this, &MainWindow::close);
    //显示参数设置对话框
    connect(ui->actionOption, &QAction::triggered, m_settingDialog, &QDialog::show);

    connect(ui->actionAbout, &QAction::triggered, [=]() {
        QMessageBox::aboutQt(this, "About Qt");
    });
}

//构建请求报文
QModbusDataUnit MainWindow::readRequest() const
{
    //const auto type = static_cast<QModbusDataUnit::RegisterType>(ui->cbRegisterType->currentData().toInt());

   QModbusDataUnit::RegisterType type = QModbusDataUnit::Invalid;

   qDebug() << ui->cbRegisterType->currentText();

   if (ui->cbRegisterType->currentText() == QString("线圈"))
   {
        type = QModbusDataUnit::Coils;
   }
   else if (ui->cbRegisterType->currentText() == QString("离散输入"))
   {
       type = QModbusDataUnit::DiscreteInputs;
   }
   else if (ui->cbRegisterType->currentText() == QString("输入寄存器"))
   {
       type = QModbusDataUnit::InputRegisters;
   }
   else if (ui->cbRegisterType->currentText() == QString("保持寄存器"))
   {
       type = QModbusDataUnit::HoldingRegisters;
   }

    qDebug() << "请求报文类型: " << type;

    //获取
    int startAddress = ui->spReadStartAddr->value();
    Q_ASSERT(startAddress >= 0 && startAddress < 10);

    quint16 numberOfEntries = ui->cbReadCount->currentText().toUShort();

    return QModbusDataUnit(type, startAddress, numberOfEntries);
}


//写请求数据包封装
QModbusDataUnit MainWindow::writeRequest() const
{
    QModbusDataUnit::RegisterType type = QModbusDataUnit::Invalid;

    qDebug() << ui->cbRegisterType->currentText();

    if (ui->cbRegisterType->currentText() == QString("线圈"))
    {
         type = QModbusDataUnit::Coils;
    }
    else if (ui->cbRegisterType->currentText() == QString("离散输入"))
    {
        type = QModbusDataUnit::DiscreteInputs;
    }
    else if (ui->cbRegisterType->currentText() == QString("输入寄存器"))
    {
        type = QModbusDataUnit::InputRegisters;
    }
    else if (ui->cbRegisterType->currentText() == QString("保持寄存器"))
    {
        type = QModbusDataUnit::HoldingRegisters;
    }

     qDebug() << "请求报文类型: " << type;

     //获取
     int startAddress = ui->sbWriteStartAddr->value();
     Q_ASSERT(startAddress >= 0 && startAddress < 10);

     quint16 numberOfEntries = ui->cbWriteCount->currentText().toUShort();

     //qDebug() << "Test: " << startAddress << " " << numberOfEntries;
     return QModbusDataUnit(type, startAddress, numberOfEntries);
}

//连接和断开连接的槽函数
void MainWindow::onConnectButtonClicked()
{
    if (!modbusDevice)
    {
        return;
    }

    //清空状态栏消息
    statusBar()->clearMessage();

    if (modbusDevice->state() != QModbusDevice::ConnectedState)
    {
        auto type = static_cast<ModbusConnection>(ui->cbConnType->currentIndex());
        if (type == Serial)
        {
            //设置串口连接信息
            modbusDevice->setConnectionParameter(QModbusDevice::SerialPortNameParameter,
                                                 m_settingDialog->settings().serialName);
            modbusDevice->setConnectionParameter(QModbusDevice::SerialParityParameter,
                                                 m_settingDialog->settings().parity);
            modbusDevice->setConnectionParameter(QModbusDevice::SerialBaudRateParameter,
                                                 m_settingDialog->settings().baud);
            modbusDevice->setConnectionParameter(QModbusDevice::SerialDataBitsParameter,
                                                 m_settingDialog->settings().dataBits);
            modbusDevice->setConnectionParameter(QModbusDevice::SerialStopBitsParameter,
                                                 m_settingDialog->settings().stopBits);
        }
        else
        {
            //TCP连接信息
            const QUrl url = QUrl::fromUserInput(ui->lineEditPort->text());
            modbusDevice->setConnectionParameter(QModbusDevice::NetworkPortParameter,
                                                 url.port());
            modbusDevice->setConnectionParameter(QModbusDevice::NetworkAddressParameter,
                                                 url.host());
        }

        modbusDevice->setTimeout(m_settingDialog->settings().responseTime);
        modbusDevice->setNumberOfRetries(m_settingDialog->settings().numberOfRetries);

        if (!modbusDevice->connectDevice())
        {
            statusBar()->showMessage(tr("Connect failed..") + modbusDevice->errorString(), 5000);
        }
        else
        {
            statusBar()->showMessage(tr("Connect Successfully"), 5000);
            qDebug() << "连接OK";
            ui->actionConnect->setEnabled(false);
            ui->actionDisconnect->setEnabled(true);

            //使能读写操作
            ui->btnRead->setEnabled(true);
            ui->btnWrite->setEnabled(true);
            ui->btnReadWrite->setEnabled(true);

        }
    }
    else
    {
        //断开连接
        modbusDevice->disconnectDevice();
        ui->actionConnect->setEnabled(true);
        ui->actionDisconnect->setDisabled(true);
        qDebug() << "断开连接成功";

        //禁用读写操作
        ui->btnRead->setEnabled(false);
        ui->btnWrite->setEnabled(false);
        ui->btnReadWrite->setEnabled(false);
    }
}


//连接类型槽函数 TCP Serial
void MainWindow::onConnectTypeChanged(int index)
{
    //如果之前存在连接，则断开连接，然后释放内存
    if(modbusDevice)
    {
        modbusDevice->disconnectDevice();
        delete modbusDevice;
        modbusDevice = nullptr;
    }

    auto type = static_cast<ModbusConnection>(index);
    if (type == Serial)
    {
        modbusDevice = new QModbusRtuSerialMaster(this);
        qDebug() << "new QModbusRtuSerialMaster Ok";
        statusBar()->showMessage("new QModbusRtuSerialMaster Ok", 3000);

    }
    else if (type == Tcp)
    {
        modbusDevice = new QModbusTcpClient(this);
        if (ui->lineEditPort->text().isEmpty())
            ui->lineEditPort->setText(QLatin1String("127.0.0.1:10086"));
    }
    else
    {
        statusBar()->showMessage("连接类型非法", 5000);
    }

    connect(modbusDevice, &QModbusClient::errorOccurred, [this](QModbusDevice::Error){
        statusBar()->showMessage(modbusDevice->errorString(), 5000);
    });

    if (!modbusDevice)
    {
        //分配空间失败
        ui->btnConnect->setDisabled(true);
        if (type == Serial)
        {
            statusBar()->showMessage(tr("创建Modbus Master失败"), 5000);
        }
        else
        {
            statusBar()->showMessage(tr("创建Modbus Client失败"), 5000);
        }
    }
    else
    {
        connect(modbusDevice, &QModbusClient::stateChanged,
                this, &MainWindow::onModbusStateChanged);
    }

}


//Modbus状态改变槽函数
void MainWindow::onModbusStateChanged(int state)
{
    //判断Modbus设备连接是否处于连接状态
    bool connected = (state != QModbusDevice::UnconnectedState);

    ui->actionConnect->setEnabled(!connected);
    ui->actionDisconnect->setEnabled(connected);

    if (QModbusDevice::UnconnectedState == state)
    {
        ui->btnConnect->setText(tr("Connect"));
    }
    else
    {
        ui->btnConnect->setText(tr("Disconnect"));
    }
}


//读操作槽函数
void MainWindow::onReadButtonClicked()
{
    if (!modbusDevice)
    {
        return;
    }

    ui->textEditRead->clear();
    statusBar()->clearMessage();

    //发送请求报文数据
    auto *reply = modbusDevice->sendReadRequest(readRequest(), ui->sbServerAddr->value());
    if (reply)
    {
        if (!reply->isFinished())
        {
            //完毕之后 自动触发槽函数
            connect(reply, &QModbusReply::finished, this, &MainWindow::onReadReady);
        }
        else
        {
            //广播消息  不需要返回响应
            delete reply;
        }
    }
    else
    {
        statusBar()->showMessage(tr("Read Error: ") + modbusDevice->errorString(), 5000);
    }


}


//读取数据
void MainWindow::onReadReady()
{
    auto reply = qobject_cast<QModbusReply*>(sender());
    if (!reply)
    {
        return;
    }

    if (reply->error() == QModbusDevice::NoError)
    {
        const QModbusDataUnit data = reply->result();
        for (int i = 0, total = (int)data.valueCount(); i < total; i++)
        {
            const QString str = tr("Address: %1 Value: %2").arg(data.startAddress() + i)
                    .arg(QString::number(data.value(i), data.registerType() <= QModbusDataUnit::Coils ? 10 : 16));
            ui->textEditRead->append(str);
        }
    }
    else if (reply->error() == QModbusDevice::ProtocolError)
    {
        statusBar()->showMessage(tr("Read response error: %1 (Modbus exception: 0x%2)").
                                 arg(reply->errorString()).
                                 arg(reply->rawResult().exceptionCode(), -1, 16), 5000);
    }
    else
    {
        statusBar()->showMessage(tr("Read response error: %1 (Code: 0x%2)").
                                 arg(reply->errorString()).
                                 arg(reply->error(), -1, 16), 5000);
    }


    //释放内存
    reply->deleteLater();
}

void MainWindow::onWriteButtonClicked()
{
    if (!modbusDevice)
    {
        return;
    }

    statusBar()->clearMessage();

    QModbusDataUnit writeData = writeRequest();
    QModbusDataUnit::RegisterType type = writeData.registerType();
    //qDebug() << "test: " << writeData.valueCount();
    for (int i = 0, total = (int)(writeData.valueCount()); i < total; i++)
    {
        if (type == QModbusDataUnit::Coils)
        {
            writeData.setValue(i, writeModel->m_coils[i + writeData.startAddress()]);
        }
        else
        {
            //qDebug() << "test: " << writeModel->m_holdingRegisters[i + writeData.startAddress()];
            writeData.setValue(i, writeModel->m_holdingRegisters[i + writeData.startAddress()]);
        }
    }

    qDebug() << "写数据内容为：" << writeData.values();

    //发送请求报文数据
    auto *reply = modbusDevice->sendWriteRequest(writeData, ui->sbServerAddr->value());
    if (reply)
    {
        if (!reply->isFinished())
        {
            //完毕之后 自动触发槽函数
            connect(reply, &QModbusReply::finished, this, [this, reply]{
                if (reply->error() == QModbusDevice::ProtocolError)
                {
                    statusBar()->showMessage(tr("Write Protocaol response error: %1").arg(reply->errorString()), 5000);
                }
                else if (reply->error() != QModbusDevice::NoError)
                {
                    statusBar()->showMessage(tr("Write response error: %1").arg(reply->errorString()), 5000);
                }
                else
                {
                    qDebug() << "写响应的数据: " << reply->result().values();
                }

                reply->deleteLater();

            });
        }
        else
        {
            //广播消息  不需要返回响应
            reply->deleteLater();
        }
    }
    else
    {
        statusBar()->showMessage(tr("Write Error: ") + modbusDevice->errorString(), 5000);
    }
}


//读写按钮槽函数
void MainWindow::onReadWriteButtonClicked()
{
    if (!modbusDevice)
    {
        return;
    }

    statusBar()->clearMessage();

    QModbusDataUnit writeData = writeRequest();
    QModbusDataUnit::RegisterType type = writeData.registerType();
    //qDebug() << "test: " << writeData.valueCount();
    for (int i = 0, total = (int)(writeData.valueCount()); i < total; i++)
    {
        if (type == QModbusDataUnit::Coils)
        {
            writeData.setValue(i, writeModel->m_coils[i + writeData.startAddress()]);
        }
        else
        {
            //qDebug() << "test: " << writeModel->m_holdingRegisters[i + writeData.startAddress()];
            writeData.setValue(i, writeModel->m_holdingRegisters[i + writeData.startAddress()]);
        }
    }

    qDebug() << "写数据内容为：" << writeData.values();

    //发送请求报文数据
    auto *reply = modbusDevice->sendReadWriteRequest(readRequest(), writeData, ui->sbServerAddr->value());
    if (reply)
    {
        if (!reply->isFinished())
        {
            connect(reply, &QModbusReply::finished, this, &MainWindow::onReadReady);

            //完毕之后 自动触发槽函数
            connect(reply, &QModbusReply::finished, this, [this, reply]{
                if (reply->error() == QModbusDevice::ProtocolError)
                {
                    statusBar()->showMessage(tr("Write Protocaol response error: %1").arg(reply->errorString()), 5000);
                }
                else if (reply->error() != QModbusDevice::NoError)
                {
                    statusBar()->showMessage(tr("Write response error: %1").arg(reply->errorString()), 5000);
                }
                else
                {
                    qDebug() << "写响应的数据: " << reply->result().values();
                }

                reply->deleteLater();

            });
        }
        else
        {
            //广播消息  不需要返回响应
            reply->deleteLater();
        }
    }
    else
    {
        statusBar()->showMessage(tr("Write Error: ") + modbusDevice->errorString(), 5000);
    }
}

void MainWindow::onWriteTableChanged(int index)
{
    const bool coilsOrHolding = index == 0 || index == 3;

    if (coilsOrHolding)
    {
        ui->treeViewWrite->setColumnHidden(1, index != 0);
        ui->treeViewWrite->setColumnHidden(2, index != 3);
        ui->treeViewWrite->resizeColumnToContents(0);
    }

    ui->btnReadWrite->setEnabled(index == 3);
    ui->btnWrite->setEnabled(coilsOrHolding);
    ui->groupBox_2->setEnabled(coilsOrHolding);
}

08. 程序下载

QModbus TCP模式写操作示例(一).rar

QModbus TCP模式综合操作(二).rar

09. 附录

9.1 Qt教程汇总
网址：https://dengjin.blog.csdn.net/article/details/115174639