Registering Server Programs on the SAP Gateway 
An RFC server program can be registered with the SAP gateway and wait for incoming RFC call requests.
This new registering feature has the following features:
An RFC server program registers itself under a programID at an SAP gateway and not for a specific SAP system.
In an SAP system, the destination must be defined with transaction SM59, using connection type T and Register Mode. Moreover, this entry must contain information about the SAP gateway at which the RFC server program is registered.
After executing an RFC function, the RFC connection is closed. If this RFC server program works with RfcListenAndDispatch in a loop (this procedure is recommended), it is automatically registered again at the same SAP gateway under the same program ID and can then wait for further RFC call requests from the same SAP system or from other SAP systems.
Procedure
AS ABAP
The following properties must be specified for the RFC destination in transaction SM59:
Connection Type T
Register Mode
RFC Server
As a registered server the RFC server uses the initial function RfcRegisterServer.
Note
If the RFC server is started by the application server, it must use the function RfcStartServer.
Security
If an RFC server is registered on an RFC gateway, it is generally possible to send calls from other SAP systems (not relevant to this gateway) or from external RFC clients to this server. If, for security reasons, the server should only be able to be called by specified systems or users, the server must implement its own logon data check and reject unwanted initiators.
Note
For detailed information on executing this logon check refer to SAP Note 1058327.
More Information
You can find general information on RFC API security issues here: