In the realm of “Energy and Sustainable Engineering,” this research introduces a pioneering strategy to enhance the security of Modbus TCP/IP communication in Industrial Control Systems (ICS). The proposed methodology integrates Fernet key-based encryption within a custom architecture, featuring a PLC serving as a Modbus TCP/IP server and a specialized Python Modbus client for communication. Additionally, a Python socket server acts as a secure intermediary between the PLC and a SCADA system. Robust encryption and decryption processes employing Fernet keys ensure the confidentiality and integrity of communication at both the socket and Modbus layers. This paper delineates the innovative approach, detailing security measures, and validation processes conducted to assess the robustness of the proposed system. Early results showcase a notable improvement in security and confidentiality within Modbus TCP/IP communication. This research harmoniously aligns with the broader themes of “Sustainable Energy” and “Engineering,” offering vital contributions to secure communication protocols in the ever-evolving landscape of sustainable energy systems.