Given the growth of IoT applications using the MQTT protocol as a base and the Node-RED platform, we have created a possibility for industrial devices or devices using Modbus RTU protocol (RS232 or RS485) to interact with applications or IoT platforms that use MQTT in This Node-RED case.In the industry there is a large number of Monitoring and Control Devices that have Modbus RTU such as Counters, Meters (Flow, Electrical, Temperature, Humidity, etc.), Industrial Controllers PLC, PAC, HMI Screens, Speed Inverters, For which the only possibility of extracting and concentrating data through OPC servers.Some of the components required for building & testing:ESP8266 12E Node MCU MAX232 (RS232 to TTL)HMI GT05 Panasonic RS232 (Any device or PLC controller that supports Modbus RTU RS232)Power supply Meanwell 5vNote:You could use any ESP8266, but in this case it is used (softwareserial), if you want to use ESP8266 01 you must modify the Modbus library to replace the “SoftwareSerial” port with the “Serial” port by default.”