modbus-proxy 0.2.0

ModBus TCP proxy

ModBus TCP proxy

Many modbus devices support only one or very few clients. This proxy acts as a bridge between the client and the modbus device. It can be seen as a layer 7 reverse proxy. This allows multiple clients to communicate with the same modbus device.

When multiple clients are connected, cross messages are avoided by serializing communication on a first come first served REQ/REP basis.

Installation

From within your favorite python 3 environment type:

$ pip install modbus-proxy

Note: On some systems pip points to a python 2 installation. You might need to use pip3 command instead.

Running the server

$ modbus-proxy -b tcp://0:9000 --modbus tcp://plc1.acme.org:502

Now, instead of connecting your client(s) to plc1.acme.org:502 you just need to tell them to connect to *machine*:9000 (where machine is the host where modbus-proxy is running).

Running the examples

To run the examples you will need to have umodbus installed (do it with pip install umodbus).

Start the simple_tcp_server.py (this will simulate an actual modbus hardware):

$ python examples/simple_tcp_server.py -b :5020

You can run the example client just to be sure direct communication works:

$ python examples/simple_tcp_client.py -a 0:5020
holding registers: [1, 2, 3, 4]

Now for the real test:

Start a modbus-proxy bridge server with:

$ modbus-proxy -b tcp://:9000 --modbus tcp://:5020

Finally run a the example client but now address the proxy instead of the server (notice we are now using port 9000 and not *5020):

$ python examples/simple_tcp_client.py -a 0:9000
holding registers: [1, 2, 3, 4]

Docker

This project ships with a basic Dockerfile which you can use as a base to launch modbus-proxy inside a docker container.

First, build the docker image with:

$ docker build -t img-modbus-proxy .

To run the container you need to set two variables:

• MODBUS_ADDRESS - the address of your modbus device (ex: tcp://plc.acme.org:502)
• MODBUS_BIND - which TCP address your server will bind to inside docker (ex: tcp://0:502)

Also you need to expose the MODBUS_BIND port.

Here is a minimum example:

$ docker run -d -p 5020:502 -e MODBUS_BIND=tcp://0:502 -e MODBUS_ADDRESS=tcp://plc.acme.org:502 img-modbus-proxy

Should be able to access your modbus device through the modbus-proxy by connecting your client(s) to <your-hostname/ip>:5020

Credits

Development Lead

• Tiago Coutinho [e-mail]

Contributors

None yet. Why not be the first?

History

0.1.0 (2020-11-11)

• First release on PyPI.