- * Ask the consumer if the data is ready to read (NOT pending) for the specific
- * session id.
- *
- * This function has a different behavior with the consumer i.e. that it waits
- * for a reply from the consumer if yes or no the data is pending.
+ * Ask the consumer if the data is pending for the specific session id.
+ * Returns 1 if data is pending, 0 otherwise, or < 0 on error.