pyModSlave is a free, Python-based Modbus slave application for simulation purposes. It supports Modbus RTU and TCP, includes a built-in bus monitor for examining all traffic on the bus, and can be run as a Pythonmodule or as a standalone GUI (Windows only — unzip and run, no installation required).
pyModSlave is based on modbus-tk, pySerial, and PyQt5.
Pythonmodule for network variables for CoDeSys PLCs
CoDeSys v2.3 supports so called network variables. Blocks of (global) variables, that propagates over networks like TCP, UDP or UDP Multicast aso.
This pythonmodule supports parsing, receiving and sending those blocks (with UDP Multicast only).
With this you can add for example a Raspberry Pi Sensor to your automation network without special Network clients on your PLC.