Introduction to Modbus TCP IP
Modbus TCP IP protocol based communication architectures (TCP / IP) client / server designed for Ethernet communication Industrial controllers PLCs. Advantages over other Industrial Protocols
1. It is public.
2. Its implementation is easy and requires little development.
3. Manages data blocks without supposing restrictions. More Information Modbus .. Wikipedia.
There are a lot of implementations of this protocol in the variety of languages Java, Python, C programming, etc.
it would seem that a lot of Industrial controllers, OPC, HMI and Scada They use Modbus TCP IP.