HiveMQ Cloud server rejects connection to ESP32

Hi, I am trying to connect to HiveMQ Cloud with an ESP32, but the mqtt server rejects the connection with the message “rc-2”. I use the WIFIClientSecure library. I need your help. Thank you very much.

Hi Omar,

Welcome to the HiveMQ Community!

You indicated that the HiveMQ Cloud broker has rejected the connection with the message “rc-2”. According to the MQTT specification, CONNACK return code 2 means “0x02 Connection Refused, identifier rejected” i.e. “The Client identifier is correct UTF-8 but not allowed by the Server”.

First step hence is to check what is the client id that your device is using.

More info on the return codes:

  1. MQTT Specification
  2. MQTT Client and Broker and MQTT Server and Connection Establishment Explained - MQTT Essentials: Part 3

Kind regards,
Dasha from HiveMQ Team