For a long time, Modbus was considered insecure, but since 2018, there has also been an improvement here to integrate secure data exchange via Modbus.
Modbus has been used in industry for decades. The abbreviation mbap stands for "Modbus Application Protocol" and appropriately in 2018 there was the update mbaps for "Modbus Security Application Protocol" in the form of a specification.
The old familiar port 502 for Modbus is still available. However, if one wants the new security, port 802 will be the connection target. In other words, IANA has provided Modbus/TCP with a secured "well known port". This should allow the integration of the secure interface to spread quickly and also to be rolled out via updates. Great news for all Modbus integrators.
Simple and proven, but also secure - this is a good step for the industry and the RetroFit to new technologies.