message-parser.rst

Modbus Message Parsing Example

This is an example of a parser to decode raw messages to a readable description. It will attempt to decode a message to the request and response version of a message if possible. Here is an example output:

$./message-parser.py -b -m 000112340006ff076d
================================================================================
Decoding Message 000112340006ff076d
================================================================================
ServerDecoder
--------------------------------------------------------------------------------
name            = ReadExceptionStatusRequest
check           = 0x0
unit_id         = 0xff
transaction_id  = 0x1
protocol_id     = 0x1234
documentation   =
    This function code is used to read the contents of eight Exception Status
    outputs in a remote device.  The function provides a simple method for
    accessing this information, because the Exception Output references are
    known (no output reference is needed in the function).

ClientDecoder
--------------------------------------------------------------------------------
name            = ReadExceptionStatusResponse
check           = 0x0
status          = 0x6d
unit_id         = 0xff
transaction_id  = 0x1
protocol_id     = 0x1234
documentation   =
    The normal response contains the status of the eight Exception Status
    outputs. The outputs are packed into one data byte, with one bit
    per output. The status of the lowest output reference is contained
    in the least significant bit of the byte.  The contents of the eight
    Exception Status outputs are device specific.

Program Source

.. literalinclude:: ../../../examples/contrib/message-parser.py

Example Messages

See the documentation for the message generator for a collection of messages that can be parsed by this utility.