HTTP is a text-based protocol to retrieve Web pages through a Web browser. Mostly, if you are on a LAN connection, you are behind a proxy server; this proxy server has one HTTP proxy running on some defined port. In your Internet Explorer's Connection option, you specify LAN settings as required. This proxy server is definitely running on a text-based protocol, and you can only get HTTP-related data from the outside network, right!! Well, there is a small loophole from which you can go through HTTP and connect to the outside world and get any data you want in binary protocol, or even your own protocol. It's through HTTPS.
In HTTPS, data is transferred from browser to server and server to browser in a secure manner. It's a binary protocol; when it goes through a proxy, the proxy doesn't understand anything. The proxy just allows a binary stream to open and lets both server and client exchange the data. Now, we can fool the proxy server and connect to any server and exchange data. The proxy server will think that we are doing some secure HTTP session.
For HTTPS, your browser connects to a proxy server and sends a command:
<FONT color=#000080><FONT color=#ff0000>CONNECT</FONT>
Then, the proxy server treats this as some HTTP Secure Session, and opens a binary stream to the required server and port as defined. If a connection is established, the proxy server returns the following response:
Now, the browser is connected to the end server and can exchange data in both a binary and secure form.
How to Do This
Now, it's your program's turn to fool the proxy server and behave as Internet Explorer behaves for Secure HTTP.
- Connect to Proxy Server first.
- Issue CONNECT Host:Port HTTP/1.1<CR><LF>.
- Issue <CR><LF>.
- Wait for a line of response. If it contains HTTP/1.X 200, the connection is successful.
- Read further lines of response until you receive an empty line.
- Now, you are connected to the outside world through a proxy. Do any data exchange you want.
Sample Source Code
Library Source Code
The Dns.h file contains all DNS-related source code. It uses other libraries, as SocketEx.h, SocketClient.h, and NeuroBuffer.h.
Socket functions as a wrapper class. (
CSocket is very heavy and unreliable if you don't have the exact idea of how it works.) All the functions are of the same name as
CSocket. You can use this class directly.
CSocketEx and throws proper exceptions with details of Winsock errors. It defines two operators,
<<, for easy sending and receiving; it also changes network to host and host to network order of bytes if required.
CSocketClient, you can call the
SetProxySettings(ProxyServer,Port) method and set proxy settings. Then, you can connect to the desired host and port as you need. The
ConnectTo method is overridden, and it automatically implements an HTTP proxy protocol and gives you a connection without any hassle.
How to Use CHttpProxySocketClient
Note: I usually don't program in the form of .h and .cpp different files, because using them the next time somewhere else is a big problem because you must move both files here and there. So, I put all the code in my .h file only; I don't write to the .cpp file unless it's required. You need to copy only the SocketEx.h, SocketClient.h, and HttpProxySocket.h files into your project's directory, and add line:
#include "<FONT color=#ff0000>HttpProxySocket.h</FONT>"
and so forth code of your Visual Studio-generated file. If you put anything above this, you will get n number of errors.
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