1) When multiple gateways are connected to one background server, and multiple 485 devices are connected to one gateway, if different gateways are connected to 485 devices with the same address number, the background server cannot distinguish which 485 slave device is, and at most The number of 485 devices can only be limited to 254, while the modbus-tcp protocol includes 4 bytes of custom message header and data length. We can identify different gateways through the message header or distinguish them by data length, thereby increasing scalability. The number of 485 devices solves the problem very well.
2) At present, the Modbus TCP/IP protocol is mainly used in the Internet or Intranet, while Ethernet has a long transmission distance and fast transmission speed, which makes it widely used. Long transmission distance and fast transmission speed make it widely used.
This picture shows the modbus TCP IP protocol temperature and humidity sensor
This picture shows the modbus RTU protocol