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 Python module or as a standalone GUI (Windows only — unzip and run, no installation required).
pyModSlave is based on modbus-tk, pySerial, and PyQt5.
...The communication with the hardware is independent of the GUI and any number of devices can be selected. To modify the code for any other task only the hardware interface needs to be redefined.
Retic is a free EAI Server written in Jython (Java).
It permits to execute adaptors composed of sources, pipes (transformations) and sinks.
Connectivity with : JMS,HTTP,SOAP,UDDI,FTP,Xindice,JDBC,Jabber,SMTP...
XML Support : XSLT, Xpath.
Has GUI for