QT技巧系列(9)QModbusTcpClient客户端程序示例及代码

QT技巧系列(9)QModbusTcpClient使用Modbus Tcp客户端程序示例及代码

本文详细介绍了采用QModbusTcpClient类作为MODBUS客户端程序的主要流程和主要函数示例代码，供大家参考。

包含文件：

#include <QModbusDataUnit>

#include <QModbusTcpClient>

#include <QModbusRtuSerialMaster>

1、首先连接到服务端

构造函数中

//QModbusClient *modbusDevice;

modbusDevice = new QModbusTcpClient(this);

connect(modbusDevice, &QModbusClient::stateChanged,

this, &loraThread::onStateChanged);//连接状态发生改变时处理函数（connect or discennect）

连接函数代码：

void loraThread::connectJzq()
{qDebug()<<"开始连接线程："<<QThread::currentThread();  //显示当前线程的数值if(!modbusDevice){return;}if(modbusDevice->state() != QModbusDevice::ConnectedState){const QUrl url = QUrl::fromUserInput("192.168.2.111:502"); //;//获取IP和端口号modbusDevice->setConnectionParameter(QModbusDevice::NetworkPortParameter, url.port());modbusDevice->setConnectionParameter(QModbusDevice::NetworkAddressParameter, url.host());modbusDevice->setTimeout(500);modbusDevice->setNumberOfRetries(3);if(!modbusDevice->connectDevice())//连接失败{isConnected = false;}else//成功连接{isConnected = true;}}else{isConnected = false;modbusDevice->disconnectDevice();//emit change2Con();}qDebug() << modbusDevice->state();}

2、发送读或写请求到服务端

写请求代码：

给QModbusDataUnit赋值后发送写请求sendWriteRequest，写到相应寄存器中的相应位置，操作成功，没有发生错误的话sendWriteRequest将返回一个QModbusReply，否则返回空指针。当reply完成或放弃后reply->isFinished()将返回true。

void loraThread::on_writeTor(QString t)
{if (!modbusDevice)return;QModbusDataUnit writeUnit = QModbusDataUnit(QModbusDataUnit::HoldingRegisters, 4, 2);for (uint i = 0; i < writeUnit.valueCount(); i++){int ii = static_cast<int>(i);int j = 4*ii;QString st = t.mid (j,4);bool ok;int hex =st.toInt(&ok,16);//将读取到的数据转换为16进制发送quint16 qhex =static_cast<quint16>(hex);// qDebug()<<writeUnit.valueCount();writeUnit.setValue(ii,qhex);}if (auto *reply = modbusDevice->sendWriteRequest(writeUnit, 1)) {//1->modbus 地址if (!reply->isFinished()) {connect(reply, &QModbusReply::finished, this, [this, reply]() {if (reply->error() == QModbusDevice::ProtocolError){emit statusBar(tr("Write response error: %1 (Mobus exception: 0x%2)").arg(reply->errorString()).arg(reply->rawResult().exceptionCode(), -1, 16));} else if (reply->error() != QModbusDevice::NoError){emit statusBar(tr("Write response error: %1 (code: 0x%2)").arg(reply->errorString()).arg(reply->error(), -1, 16));}reply->deleteLater();});} else {// broadcast replies return immediatelyreply->deleteLater();}} else {emit statusBar(tr("Write error: ") + modbusDevice->errorString());}}

读请求代码：

发送sendReadRequest读请求，成功则异步函数回调处理读回的数据，错误则进行相应的处理。代码如下：

void loraThread::readDevice()
{if(!isConnected)return;if (!modbusDevice){return;}qDebug()<<"read device";QModbusDataUnit readUnit = QModbusDataUnit(QModbusDataUnit::HoldingRegisters, 520, 50);if (auto *reply = modbusDevice->sendReadRequest(readUnit, 1))   //1->modbus设备地址{if (!reply->isFinished()){connect(reply, &QModbusReply::finished, this, &loraThread::toReadReady);}else{delete reply; // broadcast replies return immediately}}else{//emit statusBar(tr("Read error: ") + modbusDevice->errorString());}QThread::msleep(1);}

读请求成功异步回调函数处理读回的数据，参考代码如下：

void loraThread::toReadReady()
{
//QModbusReply这个类存储了来自client的数据,sender()返回发送信号的对象的指针auto reply = qobject_cast<QModbusReply *>(sender());if (!reply){return;}if (reply->error() == QModbusDevice::NoError){//处理成功返回的数据const QModbusDataUnit unit = reply->result();//quint16 stat = unit.value(1);  //状态（位与关系）。。。。。。}else if (reply->error() == QModbusDevice::ProtocolError){emit statusBar(tr("Read response error: %1 (Mobus exception: 0x%2)").arg(reply->errorString()).arg(reply->rawResult().exceptionCode(), -1, 16));}else{emit statusBar(tr("Read response error: %1 (code: 0x%2)").arg(reply->errorString()).arg(reply->error(), -1, 16));}reply->deleteLater();}

状态变化处理代码：

void loraThread::onStateChanged(int state)//连接状态发生改变时处理函数（connect or discennect）{if (state == QModbusDevice::UnconnectedState){//ui->connectButton_2->setText(tr("Connect"));isConnected = false;//emit updateCount("0,0");}else if (state == QModbusDevice::ConnectedState){//ui->connectButton_2->setText(tr("Disconnect"));isConnected = true;}
}

注：实战示例，解疑答惑。

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