Class: Modbus::TCPADU

Inherits:
Object
  • Object
show all
Defined in:
lib/modbus/adu/tcp_adu.rb

Overview

ADU (Application Data Unit) for transport over TCP

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(pdu = nil, transaction_ident = 0) ⇒ TCPADU

Initializes a new TCPADU instance.

Parameters:

  • pdu (Modbus::PDU) (defaults to: nil) —

    A PDU to preset in the ADU.



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# File 'lib/modbus/adu/tcp_adu.rb', line 17

def initialize(pdu = nil, transaction_ident = 0)
  @transaction_ident = transaction_ident
  @protocol_ident    = 0
  @unit_ident        = 0xFF # TODO configurable?
  @pdu               = pdu
end

Instance Attribute Details

#pdu ⇒ Object

Returns the value of attribute pdu.



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# File 'lib/modbus/adu/tcp_adu.rb', line 10

def pdu
  @pdu
end

#protocol_ident ⇒ Object

Returns the value of attribute protocol_ident.



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# File 'lib/modbus/adu/tcp_adu.rb', line 10

def protocol_ident
  @protocol_ident
end

#transaction_ident ⇒ Object

Returns the value of attribute transaction_ident.



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# File 'lib/modbus/adu/tcp_adu.rb', line 10

def transaction_ident
  @transaction_ident
end

#unit_ident ⇒ Object

Returns the value of attribute unit_ident.



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# File 'lib/modbus/adu/tcp_adu.rb', line 10

def unit_ident
  @unit_ident
end

Instance Method Details

#decode(type, buffer, conn) ⇒ true, false

Decodes an ADU from wire format and sets the attributes of this object.

Parameters:

  • type (Symbol) —

    The type of PDU which should be created.

  • buffer (String) —

    The bytes to decode.

  • conn (Modbus::Connection::Base) —

    An EM connection object to work on.

Returns:

  • (true, false) —

    True, if there where enough bytes in the buffer and decoding was successful.



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# File 'lib/modbus/adu/tcp_adu.rb', line 47

def decode(type, buffer, conn)
  data = ProtocolData.new buffer

  # not enough data in buffer to know the length
  return false if data.size < 6

  @transaction_ident = data.shift_word
  @protocol_ident    = data.shift_word
  length             = data.shift_word

  # not enough data in buffer according to length
  return false if data.size < length

  # Strip the consumed bytes off the buffer, thus NOT consumed bytes remain in the buffer!
  buffer.slice!(0..length + 5)

  @unit_ident = data.shift_byte
  func_code   = data.shift_byte
  @pdu        = PDU.create type, func_code, data

  return true

rescue ModbusError => error
  pdu = PDU::Exception.create func_code, error
  adu = TCPADU.new pdu, @transaction_ident
  conn.send_data adu.encode

  return false
end

#encode ⇒ String

Encodes the ADU into the wire format.

Returns:

  • (String) —

    The encoded ADU.



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# File 'lib/modbus/adu/tcp_adu.rb', line 29

def encode
  data = ProtocolData.new
  data.push_word @transaction_ident
  data.push_word @protocol_ident
  data.push_word @pdu.length + 1
  data.push_byte @unit_ident
  data.concat @pdu.encode
  data.to_buffer
end