Marc Abramowitz » Using an HTTP proxy (shown via netcat)

10/23/2007

Using an HTTP proxy (shown via netcat)

October 23rd 2007 Posted to Computers, Web

Ever wonder how applications talk to HTTP proxies? It’s simple really (like the rest of HTTP) - there’s a simple HTTP request method called CONNECT. It’s easily illustrated with a quick session of netcat:

$ nc -v proxy.foobar.com 3128
proxy.foobar.com [10.xx.xx.xxx] 3128 (?) open : Operation now in progress
CONNECT marc-abramowitz.com:80 HTTP/1.0

HTTP/1.0 200 Connection established

GET / HTTP/1.1
Host: marc-abramowitz.com

HTTP/1.1 200 OK
Date: Fri, 21 Sep 2007 00:02:34 GMT
.........

Nothing magical.

The above process can be done with a program, of course. The one I am most familiar with is called corkscrew. With it you can do things like:

$ corkscrew proxy.foobar.com 3128 marc-abramowitz.com 80
GET / HTTP/1.1
Host: marc-abramowitz.com

HTTP/1.1 200 OK
Date: Wed, 28 Nov 2007 19:03:29 GMT
...

The corkscrew program is very useful in particular with the ProxyCommand config directive in OpenSSH as discussed in my post on using SSH though an HTTP proxy.

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