An easy way to connect FileMaker (or really, any program) to many popular online services is to use the inexpensive "ExpanDrive" utility on Mac and Windows to create a local drive mapping to these services. On Windows, this mapping would be drive letter. On Mac, this mapping would be a volume.
The good news is that, once connected, you access these services as if they were a local drive.
The utility is about $50 (one time), but you can optionally pay an additional $29.95 for lifetime updates!
Expected connection types like FTP, SFTP, SSH, S3 are all supported as well as many others (see below).
Here are the services currently supported:
To setup an FTP drive, for example, here's all you fill in:
Then, once you have any drive mapped, an FTP site in the example above, you just use it like any other drive and you're working with an (S)FTP site. No third-party plug-ins or other special code necessary.
Check it out.