The message ID is a unique indicator that identifies a message. In the synchronous case, the request and response messages have different IDs. The application can access the message later using this ID.
To access the message ID, use the method GET_MESSAGE_ID of the controller object:
Get a protocol instance for the protocol IF_WSPROTOCOL_MESSAGE_ID.
To have the system return the message ID after the sender has sent a request message or the receiver has received a request message, use the method GET_MESSAGE_ID of this instance. This returns the ID using the parameter MESSAGE_ID of the type SXMSGUID.