| Value | Meaning |
|---|---|
| ConnectionAccepted0x00 | Connection accepted |
| ProtocolVersion0x01 | The Server does not support the level of the MQTT protocol requested by the Client |
| Identifier0x02 | The Client identifier is correct UTF-8 but not allowed by the Server |
| ServerUnavailable0x03 | The Network Connection has been made but the MQTT service is unavailable |
| UserNameOrPassword0x04 | The data in the user name or password is malformed |
| NotAuthorized0x05 | The Client is not authorized to connect |
Connect Return code values - 0 = accepted, the rest means refused (6-255 are reserved)