url http://example.com/modified.txt headers if-modified-since: Tue, 01 Feb 1994 12:00:00 GMT ---------- GET /modified.txt HTTP/1.1 Host: example.com Connection: close If-Modified-Since: Tue, 01 Feb 1994 12:00:00 GMT User-Agent: HTTP-Tiny/VERSION ---------- HTTP/1.1 200 OK Date: Thu, 03 Feb 1994 00:00:00 GMT Last-Modified: Wed, 02 Feb 1994 00:00:00 GMT Content-Type: text/plain Content-Length: 42 abcdefghijklmnopqrstuvwxyz1234567890abcdef