Hi Marlon,
For receiving flat files, wM service, wm.EDIINT.rules:processPayload, provides a user exit for processing payloads which are neither EDI nor XML. Content type may be something like application/octet-stream. The wM The user exit invokes your service (determined from EDINT property, wm.EDIINT.userProcessPayloadService=) to process the payload.
For sending flat files, you need a service that invokes wm.EDIINT:send (like you probalby already have for XML), but the data/contentType would be application/octet-stream instead of application/XML.
Hope this helps.
#B2B-Integration#Integration-Server-and-ESB#webMethods