I'm not at all that familiar with web service, but we do have this requirement in which, once a month, we need to retrieve some pdf files from a folder in an external server, and then attach them to their respective accounts.
Now we've already figured out how to attach these files to their respective accounts since an ID of the account is written in the file's name and we'll just have to extract it with some code logic.
However, it is the part of retrieving the files from the external service that I'm not sure how we can support.
Do we need to use REST API web service? How could we retrieve the files from the folder in the external server? Does Salesforce only allow connection to HTTPS URLs?
Any help is much appreciated. Thanks.