1) telnet port 80
$ telnet linux3.cc.ntu.edu.tw 80
2) put these headers
GET /debian/dists/etch/Release.gpg HTTP/1.1
Host: linux3.cc.ntu.edu.tw
Range: bytes=188-
If-Range: Wed, 09 May 2007 08:17:15 GMT
User-Agent: Debian APT-HTTP/1.3
3) press enter twice
4) see the result