pcpp::ModbusLayer Class Reference

#include <ModbusLayer.h>

Inheritance diagram for pcpp::ModbusLayer:

Classes
struct	ModbusReadInputRegisters

Public Types
enum class	ModbusFunctionCode : uint8_t {   ReadCoils = 1 , ReadDiscreteInputs = 2 , ReadHoldingRegisters = 3 , ReadInputRegisters = 4 ,   WriteSingleCoil = 5 , WriteSingleHoldingRegister = 6 , WriteMultipleCoils = 15 , WriteMultipleHoldingRegisters = 16 ,   ReadSlaveId = 17 , UnknownFunction = 0xFF }
	Enum class representing Modbus function codes. This enumeration defines the standard Modbus function codes used in request and response PDUs. Each value corresponds to a specific operation defined by the Modbus protocol. More...

Public Member Functions
	ModbusLayer (uint8_t *data, size_t dataLen, Layer *prevLayer, Packet *packet)
	ModbusLayer (uint16_t transactionId, uint8_t unitId)
uint16_t	getTransactionId () const
uint16_t	getProtocolId () const
uint16_t	getLength () const
uint8_t	getUnitId () const
ModbusFunctionCode	getFunctionCode () const
void	setTransactionId (uint16_t transactionId)
	set the MODBUS transaction id More...
void	setUnitId (uint8_t unitId)
	set the MODBUS header unit id More...
void	setFunctionCode (ModbusFunctionCode functionCode)
	set the MODBUS header function code More...
void	parseNextLayer () override
	Does nothing for this layer (ModbusLayer is always last)
size_t	getHeaderLen () const override
	Get the length of the MODBUS header. More...
void	computeCalculateFields () override
	Does nothing for this layer.
std::string	toString () const override
OsiModelLayer	getOsiModelLayer () const override
Public Member Functions inherited from pcpp::Layer
	~Layer () override
Layer *	getNextLayer () const
Layer *	getPrevLayer () const
ProtocolType	getProtocol () const
bool	isMemberOfProtocolFamily (ProtocolTypeFamily protocolTypeFamily) const
uint8_t *	getData () const
size_t	getDataLen () const
uint8_t *	getLayerPayload () const
size_t	getLayerPayloadSize () const
bool	isAllocatedToPacket () const
void	copyData (uint8_t *toArr) const
uint8_t *	getDataPtr (size_t offset=0) const override

Static Public Member Functions
static bool	isModbusPort (uint16_t port)
	Check if a port is a valid MODBUS port. More...

Additional Inherited Members
Protected Member Functions inherited from pcpp::Layer
template<typename T , typename... Args>
Layer *	constructNextLayer (uint8_t *data, size_t dataLen, Packet *packet, Args &&... extraArgs)
template<typename T , typename TFallback , typename... Args>
Layer *	tryConstructNextLayerWithFallback (uint8_t *data, size_t dataLen, Packet *packet, Args &&... extraArgs)
Static Protected Member Functions inherited from pcpp::Layer
template<typename T >
static bool	canReinterpretAs (const uint8_t *data, size_t dataLen)
	Check if the data is large enough to reinterpret as a type. More...

Detailed Description

Represents the MODBUS Application Protocol layer

Member Enumeration Documentation

ModbusFunctionCode

enum pcpp::ModbusLayer::ModbusFunctionCode : uint8_t

strong

Enum class representing Modbus function codes. This enumeration defines the standard Modbus function codes used in request and response PDUs. Each value corresponds to a specific operation defined by the Modbus protocol.

Enumerator
ReadCoils	Read coil status (0x01)
ReadDiscreteInputs	Read discrete input status (0x02)
ReadHoldingRegisters	Read holding registers (0x03)
ReadInputRegisters	Read input registers (0x04)
WriteSingleCoil	Write a single coil (0x05)
WriteSingleHoldingRegister	Write a single holding register (0x06)
WriteMultipleCoils	Write multiple coils (0x0F)
WriteMultipleHoldingRegisters	Write multiple holding registers (0x10)
ReadSlaveId	Report slave ID (0x11)
UnknownFunction	Unknown or unsupported function code (0xFF)

Constructor & Destructor Documentation

ModbusLayer() [1/2]

pcpp::ModbusLayer::ModbusLayer ( uint8_t *  data, size_t  dataLen, Layer *  prevLayer, Packet *  packet  )

inline

A constructor that creates the layer from an existing packet raw data

Parameters

[in]	data	A pointer to the raw data
[in]	dataLen	Size of the data in bytes
[in]	prevLayer	A pointer to the previous layer
[in]	packet	A pointer to the Packet instance where layer will be stored in

ModbusLayer() [2/2]

pcpp::ModbusLayer::ModbusLayer	(	uint16_t	transactionId,
		uint8_t	unitId
	)

A constructor that creates the layer from user inputs

Parameters

[in]	transactionId	Transaction ID
[in]	unitId	Unit ID

Member Function Documentation

getFunctionCode()

ModbusFunctionCode pcpp::ModbusLayer::getFunctionCode

(

)

const

Returns

MODBUS function code

getHeaderLen()

size_t pcpp::ModbusLayer::getHeaderLen ( ) const

inlineoverridevirtual

Get the length of the MODBUS header.

Returns

Length of the MODBUS header in bytes

Implements pcpp::Layer.

getLength()

uint16_t pcpp::ModbusLayer::getLength

(

)

const

Returns

MODBUS remaining bytes in frame starting from the unit id

Note

This is the length of the MODBUS payload + unit_id, not the entire packet

getOsiModelLayer()

OsiModelLayer pcpp::ModbusLayer::getOsiModelLayer ( ) const

inlineoverridevirtual

Returns

The OSI Model layer this protocol belongs to

Implements pcpp::Layer.

getProtocolId()

uint16_t pcpp::ModbusLayer::getProtocolId

(

)

const

Returns

MODBUS protocol id

getTransactionId()

uint16_t pcpp::ModbusLayer::getTransactionId

(

)

const

Returns

MODBUS message type

getUnitId()

uint8_t pcpp::ModbusLayer::getUnitId

(

)

const

Returns

MODBUS unit id

isModbusPort()

static bool pcpp::ModbusLayer::isModbusPort ( uint16_t  port )

inlinestatic

Check if a port is a valid MODBUS port.

Parameters

port	Port number to check

Note

MODBUS uses port 502, so this function checks if the port is equal to 502

Returns

true if the port is valid, false otherwise

setFunctionCode()

void pcpp::ModbusLayer::setFunctionCode

(

ModbusFunctionCode

functionCode

)

set the MODBUS header function code

Parameters

functionCode

function code

setTransactionId()

void pcpp::ModbusLayer::setTransactionId

(

uint16_t

transactionId

)

set the MODBUS transaction id

Parameters

transactionId

transaction id

setUnitId()

void pcpp::ModbusLayer::setUnitId

(

uint8_t

unitId

)

set the MODBUS header unit id

Parameters

unitId

unit id

toString()

std::string pcpp::ModbusLayer::toString ( ) const

overridevirtual

Returns

A string representation of the layer most important data (should look like the layer description in Wireshark)

Implements pcpp::Layer.