I’ve got video files stored as:
www.example.com/video_files/abc.flv
My application uses FlowPlayer which streams this video file to the end user.
How can I restrict access to these files only to the application within the server and prevent ppl from typing in the url/file link directly and downloading the file?
The short answer is you can’t, if the media is streamed unprotected. People with packet sniffers will always be able to dump the stream as it’s sent to their browser.
If this is really important to you, you should investigate a DRM solution. (But note that DRM is not unbreakable either.)