Member Function Documentation

QModbusClient::QModbusClient(QObject *parent = nullptr)

Constructs a Modbus client device with the specified parent.

int QModbusClient::numberOfRetries() const

Returns the number of retries a client will perform before a request fails. The default value is set to 3.

See also setNumberOfRetries().

[virtual protected] bool QModbusClient::processPrivateResponse(const QModbusResponse &response, QModbusDataUnit *data)

To be implemented by custom Modbus client implementation. The default implementation ignores response and data. It always returns false to indicate error.

[virtual protected] bool QModbusClient::processResponse(const QModbusResponse &response, QModbusDataUnit *data)

Processes a Modbus server response and stores the decoded information in data. Returns true on success; otherwise false.

QModbusReply *QModbusClient::sendRawRequest(const QModbusRequest &request, int serverAddress)

Sends a raw Modbus request. A raw request can contain anything that fits inside the Modbus PDU data section and has a valid function code. The only check performed before sending is therefore the validity check, see QModbusPdu::isValid. If no error occurred the function returns a a new valid QModbusReply; nullptr otherwise. Modbus networks may have multiple servers, each server has a unique serverAddress.

See also QModbusReply::rawResult().

QModbusReply *QModbusClient::sendReadRequest(const QModbusDataUnit &read, int serverAddress)

Sends a request to read the contents of the data pointed by read. Returns a new valid QModbusReply object if no error occurred, otherwise nullptr. Modbus network may have multiple servers, each server has unique serverAddress.

QModbusReply *QModbusClient::sendReadWriteRequest(const QModbusDataUnit &read, const QModbusDataUnit &write, int serverAddress)

Sends a request to read the contents of the data pointed by read and to modify the contents of the data pointed by write using Modbus function code QModbusPdu::ReadWriteMultipleRegisters. Returns a new valid QModbusReply object if no error occurred, otherwise nullptr. Modbus network may have multiple servers, each server has unique serverAddress.

Note: : Sending this kind of request is only valid of both read and write are of type QModbusDataUnit::HoldingRegisters.

QModbusReply *QModbusClient::sendWriteRequest(const QModbusDataUnit &write, int serverAddress)

Sends a request to modify the contents of the data pointed by write. Returns a new valid QModbusReply object if no error occurred, otherwise nullptr. Modbus network may have multiple servers, each server has unique serverAddress.

void QModbusClient::setNumberOfRetries(int number)

Sets the number of retries a client will perform before a request fails. The default value is set to 3.

Note: The new value must be greater than or equal to 0. Changing this property will only effect new requests, not already scheduled ones.

See also numberOfRetries().

void QModbusClient::setTimeout(int newTimeout)

Sets the newTimeout for this QModbusClient instance. The minimum timeout is 50 ms.

The timeout is used by the client to determine how long it waits for a response from the server. If the response is not received within the required timeout, the TimeoutError is set.

Already active/running timeouts are not affected by such timeout duration changes.

Note: Setter function for property timeout.

See also timeout.

[signal] void QModbusClient::timeoutChanged(int newTimeout)

This signal is emitted if the response is not received within the required timeout. The new response timeout for the device is passed as newTimeout.

Note: Notifier signal for property timeout.