What i mean gateway service is you have to create a custom flow service which should have service input (node) to accept/receive XML documents and then invoke the http service to post the xmldata to seperate TN servers.
And give this customer flow service url to your TP
http//localhost:5555/gateway.receive:receiveXML (similar to that)
HTH,
RMG
#Integration-Server-and-ESB#webMethods#B2B-Integration