modbus-proxy 0.4.2

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.

Additionally, if you want logging configuration:

• YAML: pip install modbus-proxy[yaml] (see below)
• TOML: pip install modbus-proxy[toml] (see below)

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.

Optionally, you can set MODBUS_LOG to log.conf, log-verbose.conf.

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

Advanced configuration

--timeout=<time in secs>

Defines modbus timeout for establishing a connection and for making REQ/REP. Time is given in seconds (or fractions of). Defaults to 10s.

--log-config-file

Logging configuration file.

If a relative path is given, it is relative to the current working directory.

If a .conf or .ini file is given, it is passed directly to logging.config.fileConfig() so the file contents must obey the Configuration file format.

A simple logging configuration (also available at log.conf) which mimics the default configuration looks like this:

[formatters]
keys=standard

[handlers]
keys=console

[loggers]
keys=root

[formatter_standard]
format=%(asctime)s %(levelname)8s %(name)s: %(message)s

[handler_console]
class=StreamHandler
formatter=standard

[logger_root]
level=INFO
handlers=console

A more verbose example logging with a rotating file handler: log-verbose.conf

If a .yml, .yaml, or .toml file is given, it is parsed as a YAML or TOML file respectively. The result is then passed to logging.config.dictConfig() so the file contents must obey the Configuration dictionary schema.

The same example above (also available at log.yml) can be achieved in YAML with:

version: 1
formatters:
  standard:
    format: "%(asctime)s %(levelname)8s %(name)s: %(message)s"
handlers:
  console:
    class: logging.StreamHandler
    formatter: standard
root:
  handlers: ['console']
  level: DEBUG

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.