1url 2 http://example.com/modified.txt 3---------- 4GET /modified.txt HTTP/1.1 5Host: example.com 6Connection: close 7If-Modified-Since: Tue, 01 Feb 1994 00:00:00 GMT 8User-Agent: HTTP-Tiny/VERSION 9 10---------- 11HTTP/1.1 200 OK 12Date: Thu, 03 Feb 1994 00:00:00 GMT 13Last-Modified: Wed, 02 Feb 1994 00:00:00 GMT 14Content-Type: text/plain 15Content-Length: 42 16 17abcdefghijklmnopqrstuvwxyz1234567890abcdef 18 19