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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
#include "modbusserver.h"
#include "modbusclient.h"
// The request must contain the start address (quint16) and the number of
// registers to read (quint16).
static constexpr int ReadRequestSize {4};
// The request must contain the start address (quint16), the number of
// registers to write (quint16), the byte count (quint8) and at least one
// register value (quint16).
static constexpr int WriteHeaderSize {5};
static constexpr int MinimumWriteRequestSize {WriteHeaderSize + 2}; // 2 payload bytes
ModbusServer::ModbusServer(QObject *parent)
: QModbusTcpServer(parent)
{
setMap({{QModbusDataUnit::HoldingRegisters, {QModbusDataUnit::HoldingRegisters, 0, 10}}});
QModbusRequest::registerDataSizeCalculator(ModbusClient::CustomRead, [](const QModbusRequest &request) {
if (!request.isValid())
return -1;
return (request.dataSize() != ReadRequestSize ? -1 : ReadRequestSize);
});
QModbusRequest::registerDataSizeCalculator(ModbusClient::CustomWrite, [](const QModbusRequest &request) {
if (!request.isValid())
return -1;
if (request.dataSize() < MinimumWriteRequestSize)
return -1;
return WriteHeaderSize + quint8(request.data().at(WriteHeaderSize - 1));
});
}
QModbusResponse ModbusServer::processPrivateRequest(const QModbusPdu &request)
{
if (!request.isValid())
return QModbusServer::processPrivateRequest(request);
//! [handle_custom_read]
if (ModbusClient::CustomRead == request.functionCode()) {
quint16 startAddress, count;
request.decodeData(&startAddress, &count);
QModbusDataUnit unit(QModbusDataUnit::HoldingRegisters, startAddress, count);
if (!data(&unit)) {
return QModbusExceptionResponse(request.functionCode(),
QModbusExceptionResponse::IllegalDataAddress);
}
return QModbusResponse(request.functionCode(), startAddress, quint8(count * 2), unit.values());
}
//! [handle_custom_read]
//! [handle_custom_write]
if (ModbusClient::CustomWrite == request.functionCode()) {
quint8 byteCount;
quint16 startAddress, numberOfRegisters;
request.decodeData(&startAddress, &numberOfRegisters, &byteCount);
if (byteCount % 2 != 0) {
return QModbusExceptionResponse(request.functionCode(),
QModbusExceptionResponse::IllegalDataValue);
}
const QByteArray pduData = request.data().remove(0, WriteHeaderSize);
QDataStream stream(pduData);
QList<quint16> values;
for (int i = 0; i < numberOfRegisters; i++) {
quint16 tmp;
stream >> tmp;
values.append(tmp);
}
if (!writeData({QModbusDataUnit::HoldingRegisters, startAddress, values})) {
return QModbusExceptionResponse(request.functionCode(),
QModbusExceptionResponse::ServerDeviceFailure);
}
return QModbusResponse(request.functionCode(), startAddress, numberOfRegisters);
}
//! [handle_custom_write]
return QModbusServer::processPrivateRequest(request);
}