PETEP is an open-source Java application with graphical user interface. It allows testers to setup proxies and interceptors to manage the traffic transmitted between client and server. Currently only TCP and basic HTTP & Websocket protocols are supported (with SSL/TLS support), but other protocols might be implemented easily using extensions.
In this guide, you will get to know how PETEP works and after reading through it, you should be able to use PETEP in your penetration testing projects. However, if you have any questions, do not hesitate and write me a message.
I also recommend checking the User Guide on Youtube.