The original use case was that one (virtual) FTP server could be set up per customer, e.g. at ftp://customer01.contoso.com/stock/. This was easy for the custom

The original use case was that one (virtual) FTP server could be set up per customer, e.g. at ftp://customer01.contoso.com/stock/. This was easy for the customer to upload their .csv onto (at their own convenience, and their own schedule). How would you set up this push-based flow?