Check file before to download

Question

We suppose i have a local file in my sdcard, that an Android app did downloaded and stored, in any time in the remote server this file can change (the content) although the file name is the same.

How can i check the file versions without download the file?

Answer 1

304 Not Modified http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

Get the date from the version of the file on the SD card and ask the server if / for versions newer than that date.