Note when using MQTT:

1）AT+CLIENT cannot be set to NULL

2) AT+SERVADDR length should not exceed 21 bytes

3) It is not recommended to use a domain name, as it will take a long time for the MQTT service to resolve the domain name for the first time and increase power consumption. It is recommended to use IP instead of domain name.

If you don't know the domain name IP, you can enter the command AT+QNDS to resolve the domain name when it is not working (this process may take a long time).

Example: