Modbus is a serial communication protocol developed primarily for transmitting data between electronic devices in industrial applications. Modbus was first introduced in 1979 and has since become a widely used standard. The communication follows a server-client model, and there are two main versions: one for the serial interface and one for Ethernet. Three different operating modes are distinguished for data transmission: Modbus RTU, Modbus ASCII and Modbus TCP. These modes facilitate easy exchange of data between different devices, irrespective of their manufacturer and model. The protocol is particularly suitable for controlling processes that require data from multiple sources, such as monitoring and controlling production plants or building automation systems. Modbus is reliable, cost-effective, and can be operated at different transmission speeds. Devices with Modbus are commonly found in households, controlling energy systems such as inverters, battery charging systems, or even in e-mobility. Bidirectional integration with other systems takes place via gateways, which are widely available.