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=== Payload === Payload may contain lot of information, from networking diagnostics to application data or commands. The approach in shown this document looks similar to ModBus === ModBus === ModBus is a serial communication protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Simple and robust, it has since become a ''de facto'' standard communication protocol, and it is now a commonly available means of connecting industrial electronic devices. The main reasons for the use of ModBus in the industrial environment are: * It has been developed with industrial applications in mind * It is openly published and royalty-free * It is easy to deploy and maintain * It moves raw bits or words without placing many restrictions on vendors ModBus allows for communication between many (approximately 240) devices connected to the same network, for example a system that measures temperature and humidity and communicates the results to a computer. ModBus is often used to connect a supervisory computer with a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems. Many of the data types are named from its use in driving relays: a single-bit physical output is called a ''coil'', and a single-bit physical input is called a ''discrete input'' or a ''contact''. === ModBus Limitations === Form the point of view of WINE, ModBus has several limitations: * 240 devices are not enough for WINE; * WINE network is a more structured than simple master-slave connection; * Data types may be much more complex than ones described in ModBus. In other words, ModBus is just, from the point of view of this document, an inspiring protocol.

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