PLC4X
· PLC4X is an effort to create a universal library for accessing industrial programmable logic controllers
using a variety of protocols using a uniform API.
Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window plc4x-parent-0.10.0.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.