Function paho_mqtt_sys::MQTTAsync_unsubscribe

pub unsafe extern "C" fn MQTTAsync_unsubscribe(
    handle: MQTTAsync, 
    topic: *const c_char, 
    response: *mut MQTTAsync_responseOptions
) -> c_int

This function attempts to remove an existing subscription made by the specified client. @param handle A valid client handle from a successful call to MQTTAsync_create(). @param topic The topic for the subscription to be removed, which may include wildcards (see @ref wildcard). @param response A pointer to a response options structure. Used to set callback functions. @return ::MQTTASYNC_SUCCESS if the subscription is removed. An error code is returned if there was a problem removing the subscription.