modbus

package

v0.9.0 Latest Latest Go to latest Published: Apr 9, 2026 License: BSD-3-Clause, GPL-3.0 Imports: 8 Imported by: 0

Details

Valid go.mod file
Redistributable license
Tagged version
Stable version
Learn more about best practices

Repository

github.com/dreadl0ck/netcap

Links

Open Source Insights

Documentation ¶

Index ¶

Constants
Variables
func GetExceptionCodeName(code uint8) string
func GetFunctionCodeName(code uint8) string
func IsCriticalFunction(code uint8) bool
func IsDiagnosticFunction(code uint8) bool

Constants ¶

View Source

const (
	// Bit access - Single bits
	FuncReadCoils          = 0x01 // Read Coils (outputs)
	FuncReadDiscreteInputs = 0x02 // Read Discrete Inputs

	// Bit access - Multiple bits
	FuncWriteSingleCoil    = 0x05 // Write Single Coil
	FuncWriteMultipleCoils = 0x0F // Write Multiple Coils

	// 16-bit access - Single registers
	FuncReadHoldingRegisters = 0x03 // Read Holding Registers
	FuncReadInputRegisters   = 0x04 // Read Input Registers
	FuncWriteSingleRegister  = 0x06 // Write Single Register

	// 16-bit access - Multiple registers
	FuncWriteMultipleRegisters     = 0x10 // Write Multiple Registers
	FuncReadWriteMultipleRegisters = 0x17 // Read/Write Multiple Registers
	FuncMaskWriteRegister          = 0x16 // Mask Write Register
	FuncReadFIFOQueue              = 0x18 // Read FIFO Queue

	// File record access
	FuncReadFileRecord  = 0x14 // Read File Record
	FuncWriteFileRecord = 0x15 // Write File Record

	// Diagnostics
	FuncReadExceptionStatus   = 0x07 // Read Exception Status
	FuncDiagnostic            = 0x08 // Diagnostic
	FuncGetCommEventCounter   = 0x0B // Get Comm Event Counter
	FuncGetCommEventLog       = 0x0C // Get Comm Event Log
	FuncReportSlaveID         = 0x11 // Report Slave ID
	FuncEncapsulatedInterface = 0x2B // Encapsulated Interface Transport (includes Read Device Identification)

)

Modbus Function Codes (standard functions per Modbus Application Protocol Specification V1.1b3)

View Source

const (
	DiagReturnQueryData                = 0x00
	DiagRestartCommunications          = 0x01
	DiagReturnDiagnosticRegister       = 0x02
	DiagChangeASCIIInputDelimiter      = 0x03
	DiagForceListenOnlyMode            = 0x04
	DiagClearCountersAndDiagnosticReg  = 0x0A
	DiagReturnBusMessageCount          = 0x0B
	DiagReturnBusCommunicationError    = 0x0C
	DiagReturnBusExceptionErrorCount   = 0x0D
	DiagReturnSlaveMessageCount        = 0x0E
	DiagReturnSlaveNoResponseCount     = 0x0F
	DiagReturnSlaveNAKCount            = 0x10
	DiagReturnSlaveBusyCount           = 0x11
	DiagReturnBusCharacterOverrunCount = 0x12
	DiagClearOverrunCounter            = 0x14
)

Diagnostic sub-function codes

View Source

const (
	ExceptionIllegalFunction         = 0x01
	ExceptionIllegalDataAddress      = 0x02
	ExceptionIllegalDataValue        = 0x03
	ExceptionSlaveDeviceFailure      = 0x04
	ExceptionAcknowledge             = 0x05
	ExceptionSlaveDeviceBusy         = 0x06
	ExceptionNegativeAcknowledge     = 0x07
	ExceptionMemoryParityError       = 0x08
	ExceptionGatewayPathUnavailable  = 0x0A
	ExceptionGatewayTargetNoResponse = 0x0B
)

Exception codes

Variables ¶

View Source

var Decoder = &decoder.StreamDecoder{
	Type:        types.Type_NC_Modbus,
	Name:        serviceModbus,
	Description: "Modbus is a serial communications protocol for ICS/SCADA PLCs and industrial devices",
	PostInit: func(d *decoder.StreamDecoder) error {
		var err error
		modbusLog, _, err = logging.InitZapLogger(
			decoderconfig.Instance.Out,
			"modbus",
			decoderconfig.Instance.Debug,
		)
		return err
	},
	CanDecode: func(client, server []byte) bool {

		return canDecodeModbus(client) || canDecodeModbus(server)
	},
	DeInit: func(sd *decoder.StreamDecoder) error {
		return modbusLog.Sync()
	},
	Factory: &modbusReader{},
	Typ:     core.TCP,
}

Decoder for protocol analysis and writing audit records to disk.

Functions ¶

func GetExceptionCodeName ¶

func GetExceptionCodeName(code uint8) string

GetExceptionCodeName returns the human-readable name for a Modbus exception code.

func GetFunctionCodeName ¶

func GetFunctionCodeName(code uint8) string

GetFunctionCodeName returns the human-readable name for a Modbus function code.

func IsCriticalFunction ¶

func IsCriticalFunction(code uint8) bool

IsCriticalFunction returns true if the function code is a write operation.

func IsDiagnosticFunction ¶

func IsDiagnosticFunction(code uint8) bool

IsDiagnosticFunction returns true if the function code is a diagnostic operation.

Types ¶

This section is empty.

Source Files ¶

View all Source files

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