Hi,
Looks like you'll need some passive tapping hardware and dedicated capture
hardware to pull this one off. Then that capture tool must write a capture
file in one of the many formats Wireshark understands. Then Wireshark needs to
understand how to to read this information. the MODBUS part should be no
problem, that is found in MODBUS/TCP as well, but the serial line protocol
uses another envelope. That support has to be build in.
So, no 'off the shelf' solution this way.
Thanx,
Jaap
Niko Kozobolidis wrote:
Dear Wireshark-users:
Our Nicaraguan non-profit development organization is in the process of
trying to determine a operator panel periodic freeze. This operator
panel receives instructions from a controller. The operating panel and
controller automate the operations of a 930 kW small hydro plant that
provides electricity to a number of rural towns and villages.
The representative of the control system in Finland indicates that we
should tap directly into the cable that sends data back and forth
between the AC800M controller and the 235 Operator Panel. This is a
special cable that has a female 9-pin RS-232 plug on one end and an
RJ-45 male plug on the other end. A direct serial connection. How can
one capture Modbus traffic or in other words obtain a trace file from
this serial connection?
The control system representative also says that the software must
support “MODBUS” protocol. When you open the Wireshark main page, and
drop-down the HELP menu, there is a part of the HELP that gives a list
of “ 911 protocols and packet types supported by Wireshark”. On this
list we find “MODBUS/TCP” but not “MODBUS”. The representative from
Finland thinks that “MODBUS” is different from “MODBUS/TCP”, and that we
need Wireshark to support the “MODBUS” protocol to analyze the
AC800M-to-Operator Panel traffic. Is Modbus/Tcp different from Modbus
and if so can wireshark capture traffic in the Modbus protocol or
possibly translate from one protocol to the other?
Thank you for your help,
Cheers,
Niko
*Niko Kozobolidis, P. Eng. *
*ATDER-BL
*
