You can configure direct inbound processing which always runs via the ALE services.
General Definitions
Creating a Function Module (Direct Inbound Processing)
Maintaining the Attributes of a Function Module
Assigning a Function Module (Direct Inbound Processing)
Assigning a Process Code (Direct Inbound Processing)
Defining a Partner (Direct Inbound Processing)
Creating a Task (Exception)
Testing Inbound Processing
Testing Exception Handling