class QModbusServer¶

The QModbusServer class is the interface to receive and process Modbus requests. More…

Inherited by: QModbusTcpServer, QModbusRtuSerialServer

Synopsis¶

Methods¶

def __init__()
def data()
def serverAddress()
def setData()
def setServerAddress()

Virtual methods¶

def processPrivateRequest()
def processRequest()
def processesBroadcast()
def readData()
def setMap()
def setValue()
def value()
def writeData()

Signals¶

def dataWritten()

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description¶

Modbus networks can have multiple Modbus servers. Modbus Servers are read/written by a Modbus client represented by QModbusClient . QModbusServer communicates with a Modbus backend, providing users with a convenient API.

class Option¶

Each Modbus server has a set of values associated with it, each with its own option.

The general purpose options (and the associated types) are:

Constant

Description

QModbusServer.DiagnosticRegister

The diagnostic register of the server. quint16

QModbusServer.ExceptionStatusOffset

The exception status byte offset of the server. quint16

QModbusServer.DeviceBusy

Flag to signal the server is engaged in processing a long-duration program command. quint16

QModbusServer.AsciiInputDelimiter

The Modbus ASCII end of message delimiter. char

QModbusServer.ListenOnlyMode

Flag to set listen only mode of the server. This function is typically supported only by Modbus serial devices. bool

QModbusServer.ServerIdentifier

The identifier of the server, not the server address. quint8

QModbusServer.RunIndicatorStatus

The run indicator of the server. quint8

QModbusServer.AdditionalData

The additional data of the server. QByteArray

QModbusServer.DeviceIdentification

The physical and functional description of the server. QModbusDeviceIdentification

Constant	Description
QModbusServer.DiagnosticRegister	The diagnostic register of the server. `quint16`
QModbusServer.ExceptionStatusOffset	The exception status byte offset of the server. `quint16`
QModbusServer.DeviceBusy	Flag to signal the server is engaged in processing a long-duration program command. `quint16`
QModbusServer.AsciiInputDelimiter	The Modbus ASCII end of message delimiter. `char`
QModbusServer.ListenOnlyMode	Flag to set listen only mode of the server. This function is typically supported only by Modbus serial devices. `bool`
QModbusServer.ServerIdentifier	The identifier of the server, not the server address. `quint8`
QModbusServer.RunIndicatorStatus	The run indicator of the server. `quint8`
QModbusServer.AdditionalData	The additional data of the server. `QByteArray`
QModbusServer.DeviceIdentification	The physical and functional description of the server. `QModbusDeviceIdentification`

User options:

Constant

Description

QModbusServer.UserOption

The first option that can be used for user-specific purposes.

Constant	Description
QModbusServer.UserOption	The first option that can be used for user-specific purposes.

For user options, it is up to the developer to decide which types to use and ensure that components use the correct types when accessing and setting values.

__init__([parent=None])¶

Parameters:: parent – QObject

Constructs a Modbus server with the specified parent.

data(newData)¶

Parameters:: newData – QModbusDataUnit
Return type:: bool

Returns the values in the register range given by newData.

newData must provide a valid register type, start address and valueCount. The returned newData will contain the register values associated with the given range.

If newData contains a valid register type but a negative start address the entire register map is returned and newData appropriately sized.

See also

setData()

data(table, address, data)

Parameters:

table – RegisterType
address – int
data – quint16

Return type:

bool

Reads data stored in the Modbus server. A Modbus server has four tables (table) and each have a unique address field, which is used to read data from the desired field. See RegisterType for more information about the different tables. Returns false if address is outside of the map range or the register type is not even defined.

See also

RegisterType setData()

dataWritten(table, address, size)¶

Parameters:

table – RegisterType
address – int
size – int

This signal is emitted when a Modbus client has written one or more fields of data to the Modbus server. The signal contains information about the fields that were written:

Register type (table) that was written,

address of the first field that was written,

and size of consecutive fields that were written starting from address.

The signal is not emitted when the to-be-written fields have not changed due to no change in value.

processPrivateRequest(request)¶

Parameters:: request – QModbusPdu
Return type:: QModbusResponse

This function should be implemented by custom Modbus servers. It is called by processRequest() if the given request is not a standard Modbus request.

Overwriting this function allows handling of additional function codes and subfunction-codes not specified in the Modbus Application Protocol Specification 1.1b. Reimplementations should call this function again to ensure an exception response is returned for all unknown function codes the custom Modbus implementation does not handle.

This default implementation returns a QModbusExceptionResponse with the request function code and error code set to illegal function.

See also

processRequest()

processRequest(request)¶

Parameters:: request – QModbusPdu
Return type:: QModbusResponse

Processes a Modbus client request and returns a Modbus response. This function returns a QModbusResponse or QModbusExceptionResponse depending on the nature of the request.

The default implementation of this function handles all standard Modbus function codes as defined by the Modbus Application Protocol Specification 1.1b. All other Modbus function codes not included in the specification are forwarded to processPrivateRequest() .

The default handling of the standard Modbus function code requests can be overwritten by reimplementing this function. The override must handle the request type in question and return the appropriate QModbusResponse . A common reason might be to filter out function code requests for data values to limit read/write access and function codes not desired in particular implementations such as serial line diagnostics on ethernet or Modbus Plus transport layers. Every other request type should be forwarded to this default implementation.

Note

This function should not be overridden to provide a custom implementation for non-standard Modbus request types.

See also

processPrivateRequest()

processesBroadcast()¶

Return type:: bool

Subclasses should implement this function if the transport layer shall handle broadcasts. The implementation then should return true if the currently processed request is a broadcast request; otherwise false. The default implementation returns always false.

Note

The return value of this function only makes sense from within processRequest() or processPrivateRequest() , otherwise it can only tell that the last request processed was a broadcast request.

readData(newData)¶

Parameters:: newData – QModbusDataUnit
Return type:: bool

Reads the values in the register range given by newData and writes the data back to newData. Returns true on success or false if newData is 0, the newData range is outside of the map range or the registerType() does not exist.

Note

Sub-classes that implement reading from a different backing store then default one, also need to implement setMap() and writeData() .

See also

setMap() writeData()

serverAddress()¶

Return type:: int

Returns the address of this Modbus server instance.

See also

setServerAddress()

setData(unit)¶

Parameters:: unit – QModbusDataUnit
Return type:: bool

Writes newData to the Modbus server map. Returns false if the newData range is outside of the map range.

If the call was successful the dataWritten() signal is emitted. Note that the signal is not emitted when the addressed register has not changed. This may happen when newData contains exactly the same values as the register already. Nevertheless this function returns true in such cases.

See also

data()

setData(table, address, data)

Parameters:

table – RegisterType
address – int
data – int

Return type:

bool

Writes data to the Modbus server. A Modbus server has four tables (table) and each have a unique address field, which is used to write data to the desired field. Returns false if address outside of the map range.

If the call was successful the dataWritten() signal is emitted. Note that the signal is not emitted when data has not changed. Nevertheless this function returns true in such cases.

See also

RegisterType data() dataWritten()

setMap(map)¶

Parameters:: map – Dictionary with keys of type .QModbusDataUnit.RegisterType and values of type QModbusDataUnit.
Return type:: bool

Sets the registered map structure for requests from other ModBus clients to map. The register values are initialized with zero. Returns true on success; otherwise false.

If this function is not called before connecting, a default register with zero entries is setup.

Note

Calling this function discards any register value that was previously set.

setServerAddress(serverAddress)¶

Parameters:: serverAddress – int

Sets the address for this Modbus server instance to serverAddress.

See also

serverAddress()

setValue(option, value)¶

Parameters:

option – int
value – object

Return type:

bool

Sets the newValue for option and returns true on success; false otherwise.

Note

If the option’s associated type is quint8 or quint16 and the type of newValue is larger, the data will be truncated or conversation will fail.

Key	Description
`DiagnosticRegister`	Sets the diagnostic register of the server in a device specific encoding to `newValue`. The default value preset is `0x0000`. The bit values of the register need device specific documentation.
`ExceptionStatusOffset`	Sets the exception status byte offset of the server to `newValue` which is the absolute offset address in the coils (0x register). Modbus register table starting with `0x0000h`. The default value preset is `0x0000`, using the exception status coils similar to Modicon 984 CPUs (coils 1-8). The function returns `true` if the coils register contains the 8 bits required for storing and retrieving the status coils, otherwise `false`.
`DeviceBusy`	Sets a flag that signals that the server is engaged in processing a long-duration program command. Valid values are `0x0000` (not busy) and `0xffff` (busy). The default value preset is `0x0000`.
`AsciiInputDelimiter`	The `newValue` becomes the end of message delimiter for future Modbus ASCII messages. The default value preset is `\n`.
`ListenOnlyMode`	Ss the server’s listen only state to `newValue`. If listen only mode is set to `true`, messages are monitored but no response will be sent. The default value preset is `false`.
`ServerIdentifier`	Sets the server’s manufacturer identifier to `newValue`. Possible values are in the range of `0x00` to 0xff. The default value preset is `0x0a`.
`RunIndicatorStatus`	Sets the servers’ run indicator status to `newValue`. This data is used as addendum by the `ReportServerId` function code. Valid values are `0x00` (OFF) and `0xff` (ON). The default value preset is `0xff` (ON).
`AdditionalData`	Sets the server’s additional data to `newValue`. This data is used as addendum by the `ReportServerId` function code. The maximum data size cannot exceed 249 bytes to match response message size restrictions. The default value preset is `Qt Modbus Server`.
`DeviceIdentification`	Sets the server’s physical and functional description. By default there is no additional device identification data set.
`UserOption`	Sets the value of a user option to `newValue`. Note For user options, it is up to the developer to decide which types to use and ensure that components use the correct types when accessing and setting values.

See also

value()

value(option)¶

Parameters:: option – int
Return type:: object

Returns the value for option or an invalid QVariant if the option is not set.

Option

Description

DiagnosticRegister

Returns the diagnostic register value of the server. The diagnostic register contains device specific contents where each bit has a specific meaning.

ExceptionStatusOffset

Returns the offset address of the exception status byte location in the coils register.

DeviceBusy

Returns a flag that signals if the server is engaged in processing a long-duration program command.

AsciiInputDelimiter

Returns a end of message delimiter of Modbus ASCII messages.

ListenOnlyMode

Returns the server’s listen only state. Messages are monitored but no response will be sent.

ServerIdentifier

Returns the server manufacturer’s identifier code. This can be an arbitrary value in the range of 0x00 to 0xff.

RunIndicatorStatus

Returns the server’s run indicator status. This data is used as addendum by the ReportServerId function code.

AdditionalData

Returns the server’s additional data. This data is used as addendum by the ReportServerId function code.

DeviceIdentification

Returns the server’s physical and functional description.

UserOption

Returns the value of a user option.

Note

For user options, it is up to the developer to decide which types to use and ensure that components use the correct types when accessing and setting values.

See also

setValue()

Option	Description
`DiagnosticRegister`	Returns the diagnostic register value of the server. The diagnostic register contains device specific contents where each bit has a specific meaning.
`ExceptionStatusOffset`	Returns the offset address of the exception status byte location in the coils register.
`DeviceBusy`	Returns a flag that signals if the server is engaged in processing a long-duration program command.
`AsciiInputDelimiter`	Returns a end of message delimiter of Modbus ASCII messages.
`ListenOnlyMode`	Returns the server’s listen only state. Messages are monitored but no response will be sent.
`ServerIdentifier`	Returns the server manufacturer’s identifier code. This can be an arbitrary value in the range of `0x00` to 0xff.
`RunIndicatorStatus`	Returns the server’s run indicator status. This data is used as addendum by the `ReportServerId` function code.
`AdditionalData`	Returns the server’s additional data. This data is used as addendum by the `ReportServerId` function code.
`DeviceIdentification`	Returns the server’s physical and functional description.
`UserOption`	Returns the value of a user option. Note For user options, it is up to the developer to decide which types to use and ensure that components use the correct types when accessing and setting values.

writeData(unit)¶

Parameters:: unit – QModbusDataUnit
Return type:: bool

Writes newData to the Modbus server map. Returns true on success, or false if the newData range is outside of the map range or the registerType() does not exist.

Note

Sub-classes that implement writing to a different backing store then default one, also need to implement setMap() and readData() . The dataWritten() signal needs to be emitted from within the functions implementation as well.

See also

setMap() readData() dataWritten()