typedef axl_bool(* MyQttOnUnSubscribeHandler)(MyQttCtx *ctx, MyQttConn *conn, const char *topic_filter, axlPointer user_data)

Async notification handler that is called to notify that a unsubscribe request has been received.

The function can return axl_false to deny unsubscription, but this is highly not recommended because this will break MQTT standard where you cannot refuse processing an unsubscribe operation.

It can also be used as a way to track subscription/unsubscription taking place.

ctxThe context wherethe operation takes place.
connThe connection where the UNSUBACK request was received.
topic_filterThe topic filter requested on the UNSUBACK packet.
user_dataUser defined pointer received on the function and provided at the configuration handler.
The handler must return axl_true to accept unsubscription operation, otherwise, axl_false can be returned (NOT RECOMMENDED) to ignore request to unsubscribe.