Message Client API in SAP BODS

Hi,

             What is Message Client API in SAP BODS?. How an external application can access BODS real time job by using Message Client API. And also vice versa. What are the configurations we need to do for using Message Client API?. How to Use the functions of Message Client API like Connect, Invoke in BODS to send message to Message Client API and to receive message from Message Client API.

Regards