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Qt中的Modbus通信指南：QModbusClient与QModbusServer类解析 (qq.com)

#include <QCoreApplication>
#include <QModbusTcpServer>
#include <QUrl>

int main(int argc, char *argv[]) {
    QCoreApplication app(argc, argv);

    QModbusTcpServer modbusServer;
    // 初始化数据模型，这里我们只设置了一个保持寄存器
    QModbusDataUnitMap dataModel;
    dataModel.insert(QModbusDataUnit::HoldingRegisters, { QModbusDataUnit::HoldingRegisters, 0, 10 });
    modbusServer.setDataMap(dataModel);

    const QUrl url = QUrl::fromUserInput("127.0.0.1:502");
    modbusServer.setConnectionParameter(QModbusDevice::NetworkPortParameter, url.port());
    modbusServer.setConnectionParameter(QModbusDevice::NetworkAddressParameter, url.host());

    if (!modbusServer.listen()) {
        qFatal("Unable to start the Modbus server: %s", qPrintable(modbusServer.errorString()));
    }

    return app.exec();
}

#include <QCoreApplication>
#include <QModbusTcpClient>
#include <QModbusReply>

int main(int argc, char *argv[]) {
    QCoreApplication app(argc, argv);

    QModbusTcpClient modbusClient;
    modbusClient.setConnectionParameter(QModbusDevice::NetworkPortParameter, 502);
    modbusClient.setConnectionParameter(QModbusDevice::NetworkAddressParameter, "127.0.0.1");

    if (!modbusClient.connectDevice()) {
        qFatal("Unable to connect to the Modbus server.");
    }

    // 构建一个写请求
    QModbusDataUnit writeUnit(QModbusDataUnit::HoldingRegisters, 0, 1);
    writeUnit.setValue(0, 42); // 写入值 42 到地址 0

    if (auto *reply = modbusClient.sendWriteRequest(writeUnit, 1)) { // 1 是服务器地址
        if (!reply->isFinished()) {
            QObject::connect(reply, &QModbusReply::finished, [&]() {
                if (reply->error() == QModbusDevice::NoError) {
                    qDebug("Write success.");

                    // 构建一个读请求
                    QModbusDataUnit readUnit(QModbusDataUnit::HoldingRegisters, 0, 1);
                    if (auto *readReply = modbusClient.sendReadRequest(readUnit, 1)) {
                        if (!readReply->isFinished()) {
                            QObject::connect(readReply, &QModbusReply::finished, [readReply]() {
                                if (readReply->error() == QModbusDevice::NoError) {
                                    const QModbusDataUnit unit = readReply->result();
                                    qDebug("Read success: %d", unit.value(0));
                                } else {
                                    qWarning("Read error: %s", qPrintable(readReply->errorString()));
                                }
                                readReply->deleteLater();
                            });
                        } else {
                            delete readReply; // broadcast reply returns immediately
                        }
                    }
                } else {
                    qWarning("Write error: %s", qPrintable(reply->errorString()));
                }
                reply->deleteLater();
            });
        } else {
            delete reply; // broadcast reply returns immediately
        }
    }

    return app.exec();
}