vsPLC is a software PLC developed in node-red with a light and clean dashboard to monitor the PLC status and the memory registers set via Modbus TCP. The vsPLC purpouse is to have a virtual ModbusTCP PLC that can be used in lab to simulate a real PLC.

vsPLC can be programmed via ModbusTCP, it listen for ModbusTCP commands on port TCP/502 (it can be customized in node-red configuration). The vsPLC has four Holding Registers (address from 0 to 3) that can be set with integer values (0–255) and five Coil Registers that can be set with 0 or 1 bits values. Device ID is set to 1. More Registers can be added if needed.

The dashboard shows the registers current values:

• Coil Registers are showed on left side of the dashboard, each register value is showed (1/0).
• Holding Registers are showed in the middle of the dashboard, each register value is showed with a gauge chart (gauge values can be customized), for each register a historic chart is showed with values registered in the last minute.

Node-red need to be installed on the target machine, the following modules need to be installed before importing the vsPLC flow:

• node-red-contrib-modbus
• node-red-contrib-buffer-parser
• node-red-node-random
• node-red-dashboard
• node-red-contrib-ui-digital-clock

The procedure to import node-red modules can be find here. You can use palette manager to install all the modules. Is suggested to run node-red as a service and to start on boot.

Import the vsPLC flow json configuration into node-red, follow node-red instructions here

When using Docker, flow is automaticaly import.

# docker run --rm -p 1880:1880 -p 502:502 --name vsPLC mguyard/vsplc:latest

version: "3.3"

name: vsPLC
services:
    vsplc:
        container_name: vsPLC
        image: mguyard/vsplc:latest
        ports:
            - 1880:1880
            - 502:502
        restart: unless-stopped

Once the json flow is deployed and started vsPLC is ready to run. To open the vsPC dashboard open in a browser the page http://your_machine_ip:1880/ui (port 1880 is the node-red standard port). Https can be enabled in your node-red installation, reference here.

To set some modbus values visible in vsPLC, you can deploy a container with CLI below :

# docker run --rm -ti -e MODBUS_PLC=<your_vsPLC_docker_IP> --name modbus-client mguyard/modbus-client:latest

It's also possible to don't define environment variable -e MODBUS_PLC=<your_vsPLC_docker_IP> in Docker container creation but run.py script will require an --ip argument.

This command will prompt you a bash and you will be able to run python3 run.py if MODBUS_PLC is define in docker environment variable.

If MODBUS_PLC environement variable isn't define in Docker container, please use commande python3 run.py --ip <your_vsPLC_docker_IP>

Press Enter to stop the script