When a non-HTML file such as a PDF, DOCX, EXE, etc is made public to the WWW by an HTTP server, and a client makes a request for said file,
what facilitates the file transfer over to the client?
Is it transmitted over HTTP or another protocol? In what format or encoding is the data represented?
I'd also like to know how some file download implementations can transmit the file and simultaneously send a HTTP response back containing just the header (eg, content-disposition) which indicates to me that the empty response body was not the vessel for the file.