User Manual

3.4.1. Modbus-TCP Communication Format

Modbus-TCP:

Modbus protocol is an application layer message transmission protocol,

including three message types: ASCII, RTU, and TCP. The standard

Modbus protocol physical layer interface includes RS232, RS422, RS485

and Ethernet interfaces, and adopts master / slave communication.

Modbus TCP Communication Process:

1. Establish a TCP connection

2. Prepare Modbus messages

3. Use the send command to send a message

4. Waiting for a response under the same connection

5. Use the recv command to read the message and complete a data

exchange

6. When the communication task ends, close the TCP connection

Parameter:

Default TCP Port: 502 Protocol: 0x00 0x02

On the problem of users using communication protocols to organize

data in big endian and little endian:

In this article, data analysis is big-endian analysis.