This section describes the Modbus messaging service over TCP/IP and provides reference information to help software developers use this service. This standard does not include the encoding content of Modbus function codes. See GB/Z 19582.1-2004 "Industrial Automation Network Specifications Based on Modbus Protocol Part 1: Modbus Application Protocol" for these contents. This section describes the implementation of the Modbus messaging service. Its purpose is to facilitate interoperability between devices using the Modbus messaging service. This part mainly consists of three parts: ——Overview of Modbus protocol on TCP/IP; ——Functional description of Modbus client and server implementation; ——Recommended implementation guidelines for the object model of a Modbus implementation example.