# Interfaces - external

* **To ERP**
    * **DB communication** via Host.FromErp / Host.ToErp tables
    * **WebAPI** via HostComWebServiceServer / HostComWebServiceClient
    * **SAP IDoc;** sending and receiving SAP Idoc's
    * **SAP RFC calls;** calling RFC's in the SAP; providing RFC server for call's from SAP