Typically RFC but there are other options, please check the document below also a lot of information about Gateway features/capabilities
lot of training material: https://wiki.scn.sap.com/wiki/display/EmTech/SAP+Gateway+Self-Paced+Learning
Typically RFC but there are other options, please check the document below also a lot of information about Gateway features/capabilities
lot of training material: https://wiki.scn.sap.com/wiki/display/EmTech/SAP+Gateway+Self-Paced+Learning