How to send POST data to a webserver?

[BosseB]

It looks like the only difference is that Indy adds

Code:

Content-Transfer-Encoding: binary

just before the file data whereas FireFox does not.

As I already commented earlier, that should not affect the upload.  But I did show you exactly how to remove that header if necessary.
As I showed you on May 3rd:

Code:

Src.AddFile('update', FileName).ContentTransfer := '';

OK, I just added the final part of the Src.AddFile command as shown above.
And it resulted in a complete transfer and firmware update + IoT reboot!
So this was it!
Now working!
Thank you for your patience and advice!