Control relay using MQTT or http requests?

Is there any way how to control an Relay (Homekit MQTT 4CH 30A) using either MQTT or http requests?

I am trying to send a POST http://192.168.1.xxx/relay_do request from local network but I'm getting a response 200 with body

{"code":0,"msg":"继电器数量错误。"} 

Is there any way how to control the relay from local network?

Thanks!