Modbus and DNP3 Communication Protocols

[Steve Zhang]

For the introduction of Modbus and DNP3 protocols, please refer to:

https://scadahacker.com/library/Documents/ICS_Protocols/Triangle%20Microworks%20-%20Modbus-DNP3%20Comparison.pdf

There are some open source projects or software/tools. Here are some for your reference.

For Modbus,

• libmodbus: C. http://libmodbus.org/
• MinimalModbus: Python. https://pypi.python.org/pypi/MinimalModbus/
• pymodbus: Python. https://pypi.python.org/pypi/pymodbus
• modbut_tk: Python. https://pypi.python.org/pypi/modbus_tk

For the Modbus Master/Slave simulators:

• Modbus Pull and Slave simulator: Windows. http://www.modbustools.com/ 30 days of trial.

For DNP3,

• OpenDNP3: C/C++. https://github.com/automatak/dnp3 (2.0.x, Automatak); https://github.com/gec/dnp3 (1.1.x, Green Energy Corp)
  • Provided the Python bindings and Java bindings for OPENDNP3 libraries.
  • Provided the example codes for the DNP3 master and slave.
• DNP3 master/slave simulators:
  • TMW Protocol Test Harness: Support multiple protocols including DNP3 and Modbus. 30 days of trial. http://www.trianglemicroworks.com/products/downloads
  • Axon Test Simulator and analysis tool of protocols: Support multiple protocols including DNP3 and Modbus. Windows. Free software. http://www.axongroup.com.co/axongroupen/axon_productos_int.php?i=36

[prafull.manglic]

Hello,

A quick question.

I have a SCADA - RTU setup with DNP3 protocol for communication.

As per DNP3 specifications for Analog Input following flags will be updated.

1.online

2. Restart

3. Communications Lost

4. Remote Forced

5. Local Forced

6. OverRange

7. Reference Check

My Question is: who sets these flags? I mean whether SCADA (DNP Master) sets these flags against analog input or RTU (DNP Slave) sets these flags against analog input.

[srichivu]

All input only registers reflect the state of the corresponding physical entities.

So they are set by the slave and read by the master.

Typically master sets an input/output registrer as a control operation and the slave responds by performing some action. The result of the action could be read from some input register.

[srichivu]

https://developer.cisco.com/site/iox/docs/#dnp3

check the micro service which provides REST/Websocket API for reading data from DNP3 slave/outstation