When should one use CONNECT and GET HTTP methods at HTTP Proxy Server?

proxy httpwebrequest http-request http-proxy proxy-server
Alexsandro picture Alexsandro · Jul 28, 2012 · Viewed 84.4k times · Source

I'm building a WebClient library. Now I'm implementing a proxy feature, so I am making some research and I saw some code using the CONNECT method to request a URL.

But checking it within my web browser, it doesn't use the CONNECT method but calls the GET method instead.

So I'm confused. When I should use both methods?

Answer

Anirudh Ramanathan picture Anirudh Ramanathan · Jul 28, 2012

A CONNECT request urges your proxy to establish an HTTP tunnel to the remote end-point. Usually is it used for SSL connections, though it can be used with HTTP as well (used for the purposes of proxy-chaining and tunneling)

CONNECT www.google.com:443

The above line opens a connection from your proxy to www.google.com on port 443. After this, content that is sent by the client is forwarded by the proxy to www.google.com:443.

If a user tries to retrieve a page http://www.google.com, the proxy can send the exact same request and retrieve response for him, on his behalf.

With SSL(HTTPS), only the two remote end-points understand the requests, and the proxy cannot decipher them. Hence, all it does is open that tunnel using CONNECT, and lets the two end-points (webserver and client) talk to each other directly.

Proxy Chaining:

If you are chaining 2 proxy servers, this is the sequence of requests to be issued.

GET1 is the original GET request (HTTP URL)
CONNECT1 is the original CONNECT request (SSL/HTTPS URL or Another Proxy)

User Request ==CONNECT1==> (Your_Primary_Proxy ==CONNECT==> AnotherProxy-1 ... ==CONNECT==> AnotherProxy-n) ==GET1(IF is http)/CONNECT1(IF is https)==> Destination_URL

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