MQTT Client Connection Object Setup

Connection's Parameters

µC/MQTT-client provides the function MQTTc_ConnSetParam to configure parameters related to the MQTT Client Connection object. The function takes as argument the type of parameter and the pointer to the parameter. The following parameter types are available :

Generic Parameters

Table - MQTTc Connection Parameters

Parameter Type	Description
`MQTTc_PARAM_TYPE_BROKER_IP_ADDR`	IP Address of the MQTT broker. This field is overwritten if broker name is set.
`MQTTc_PARAM_TYPE_BROKER_NAME`	Name of the MQTT broker. This method will only work if DNS is available This field is overwritten if broker IP address is set.
`MQTTc_PARAM_TYPE_BROKER_PORT_NBR`	Sets a specific port for the MQTT broker. By default, the port is set to 1883.
`MQTTc_PARAM_TYPE_INACTIVITY_TIMEOUT_S`	Sets the Inactivity Timeout of the connection This value represents the time of inactivity allowed on a connection before it is automatically closed.
`MQTTc_PARAM_TYPE_CLIENT_ID_STR`	Connection's Client ID. This ID should be unique amongst devices connected to broker.
`MQTTc_PARAM_TYPE_USERNAME_STR`	Connection's username string. This field is optional.
`MQTTc_PARAM_TYPE_PASSWORD_STR`	Connection's password string. This field is optional.
`MQTTc_PARAM_TYPE_KEEP_ALIVE_TMR_SEC`	Connection's keep alive, in seconds. This value represent the maximal time between messages sent by the device to the broker. If no message is sent for more than this time, the broker will close the connection.
`MQTTc_PARAM_TYPE_WILL_CFG_PTR`	Pointer to will configuration. This field is optional.
`MQTTc_PARAM_TYPE_SECURE_CFG_PTR`	Pointer to secure configuration. This field is optional.
`MQTTc_PARAM_TYPE_TIMEOUT_MS`	Connection's timeout for socket 'Open', in milliseconds.
`MQTTc_PARAM_TYPE_PUBLISH_RX_MSG_PTR`	Pointer to MQTT-client message object that will be used to receive `PUBLISH` messages from broker. This parameter is mandatory.

Callback options

Table - MQTTc Connection Callbacks

Parameter Type	Description
`MQTTc_PARAM_TYPE_CALLBACK_ON_COMPL`	Sets the generic callback function to notify the application whenever an event occurs. This callback is called before every other callback and may be used in place of all the other ones.
`MQTTc_PARAM_TYPE_CALLBACK_ON_CONNECT_CMPL`	Sets the callback function to notify the application when a `CONNECT` message with the MQTT broker is completed. This parameter is optional.
`MQTTc_PARAM_TYPE_CALLBACK_ON_PUBLISH_CMPL`	Sets the callback function to notify the application when a `PUBLISH` message with the MQTT broker is completed. This parameter is optional.
`MQTTc_PARAM_TYPE_CALLBACK_ON_SUBSCRIBE_CMPL`	Sets the callback function to notify the application when a `SUBSCRIBE` message with the MQTT broker is completed. This parameter is optional.
`MQTTc_PARAM_TYPE_CALLBACK_ON_UNSUBSCRIBE_CMPL`	Sets the callback function to notify the application when an `UNSUBSCRIBE` message with the MQTT broker is completed. This parameter is optional.
`MQTTc_PARAM_TYPE_CALLBACK_ON_PINGREQ_CMPL`	Sets the callback function to notify the application when a `PINGREQ` message with the MQTT broker is completed. This parameter is optional.
`MQTTc_PARAM_TYPE_CALLBACK_ON_DISCONNECT_CMPL`	Sets the callback function to notify the application when a `DISCONNECT` message with the MQTT broker is completed. This parameter is optional.
`MQTTc_PARAM_TYPE_CALLBACK_ON_ERR_CALLBACK`	Sets the callback function to notify the application when an error with the socket connection occurs. A connection can be closed by the MQTT broker, by the client when an unexpected error occurred. To be able to re-open the socket connection and re-connect the client, this callback should be provided. This parameter is optional.
`MQTTc_PARAM_TYPE_CALLBACK_ON_PUBLISH_RX`	Sets the callback function to notify the application when a `PUBLISH` message is received from the broker. This parameter is mandatory.
`MQTTc_PARAM_TYPE_CALLBACK_ARG_PTR`	Sets the argument that will be passed to every callback function. This parameter is optional.

Example

Listing - MQTTc Connection Configuration Example

CPU_BOOLEAN  App_MQTTc_ConnPrepare (MQTTc_CONN  *p_conn)
{
    MQTTc_ERR  err;


                                                        /* ---------------- INIT NEW CONNECTION --------------- */
    MQTTc_ConnClr(p_conn, &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }
                                                        /* Set conn parameters.                                 */
    MQTTc_ConnSetParam(       &AppMQTTc_Conn,
                               MQTTc_PARAM_TYPE_BROKER_NAME,
                       (void *)APP_MQTTc_BROKER_NAME,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn,
                               MQTTc_PARAM_TYPE_CLIENT_ID_STR,
                       (void *)APP_MQTTc_CLIENT_ID_NAME,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn,
                               MQTTc_PARAM_TYPE_USERNAME_STR,
                       (void *)APP_MQTTc_USERNAME,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_PASSWORD_STR,                 
                       (void *)APP_MQTTc_PASSWORD,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_KEEP_ALIVE_TMR_SEC,           
                       (void *)1000u,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_CALLBACK_ON_COMPL,            
                       (void *)AppMQTTc_OnCmplCallbackFnct,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_CALLBACK_ON_CONNECT_CMPL,     
                       (void *)AppMQTTc_OnConnectCmplCallbackFnct,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_CALLBACK_ON_PUBLISH_CMPL,     
                       (void *)AppMQTTc_OnPublishCmplCallbackFnct,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_CALLBACK_ON_SUBSCRIBE_CMPL,   
                       (void *)AppMQTTc_OnSubscribeCmplCallbackFnct,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_CALLBACK_ON_ERR_CALLBACK,     
                       (void *)AppMQTTc_OnErrCallbackFnct,             
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(        &AppMQTTc_Conn, 
                                MQTTc_PARAM_TYPE_PUBLISH_RX_MSG_PTR,           
                       (void *)&AppMQTTc_MsgPublishRx,
                               &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_CALLBACK_ON_PUBLISH_RX,       
                       (void *)AppMQTTc_OnPublishRxCallbackFnct,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    MQTTc_ConnSetParam(       &AppMQTTc_Conn, 
                               MQTTc_PARAM_TYPE_TIMEOUT_MS,                   
                       (void *)30000u,
                              &err);
    if (err != MQTTc_ERR_NONE) {
        return (DEF_FAIL);
    }

    return (DEF_OK);
}