GitHub - jayantjpr/HTTP-Proxy: This is a very basic C/C++ http-proxy made as a part of CS345 Network Lab Course at IIT Guwahati.

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This is a very basic C/C++ http-proxy made as a part of CS345 Network Lab Course at IIT Guwahati.

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Name		Name	Last commit message	Last commit date
Latest commit History 1 Commit
Makefile		Makefile
README		README
http_header_util.cpp		http_header_util.cpp
http_header_util.h		http_header_util.h
proxy.cpp		proxy.cpp
socket_util.c		socket_util.c
socket_util.h		socket_util.h

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================================================================

    README file for Assignment 2 - HTTP Proxy

           Name:	Jayant Gupta 
      Roll No. :	10012319
     Department:	Mathematics & Computing 
 
================================================================

HOW TO USE THE PROXY
====================
1. Copy all the files in one directory.

2. On the terminal:
	~$ cd <path-to-code>
	~$ make all
	~$ ./proxy <port_number>

   --> The server should start listening for connections on the specified port.

3. Connect to the server using telnet or web-client (like web-browser).
4. Send a HTTP request, like: GET http://intranet.iitg.ernet.in/ HTTP/1.0
5. The headers and HTML of IITG Intranet Web-homepage will be displayed on the terminal screen.

EXIT THE SERVER
================
* You can exit the server by simply using Ctrl + C.

LIMITATIONS
===========
* It does not handle concurrent requests, only sequential requests.
* Only “GET” method is implemented.
* Only HTTP/1.0 requests are generated (though it accepts HTTP/1.1 requests as well).
* Connection: keep-alive not implemented.

FEATURES
========
* Accepts “GET” requests. Otherwise, responds back with a "501 Not Implemented" error.
* Flexibility in choosing the server port for the server.
* Accepts all the available formats for HTTP headers. If something goes wrong, responds with a "400 Bad Request" error.
* Works with HTTP/1.0 Also accepts HTTP/1.1 requests, but forwards the request to Web-server with HTTP version 1.0.
* Closes the client and remote server connection after a request is complete.
* Parses the given HTTP request, extarcts the hostname & Port, separates different header fields into a vector of  <Header Name, Header Value>.
* Validates the HTTP Header as well as report error to client.
* Always sends the request to Web-Server in relative path format.

IMPLEMENTATION DETAILS
=======================
I. proxy.cpp is the main file & implements the http_proxy as follows:
 	
	1.  Creates a Socket and binds it to a port --> specified as cmd-line argument.
	2.  Starts listening on the socket.
	3.  Accept connect from the client.
	4.  Receive HTTP request from the Client.
	5.  Parses/Tokenizes the HTTP Header and Checks for errors & unsupported methods. If Error in request, send the error to client.
	6.  Extracts the hostname from HTTP Header and establishes a connection over a new socket with the Web-server. 
	7.  Makes a HTTP request to the server, the HTTP Packet being in Relative path format.
	8.  Receive HTTP Response from web-server.
	9.  Forward the Response to the client. 
	10. Close the connection with client. (Web-server automatically closes connection)
	11. Wait for new connection and Goto Step 3.

II. http_header_util.cpp & http_header_util.h 
	* These files defines the class HTTPHeader and its member functions.
	* The main purpose of the HTTPHeader class is to parse & tokenize the HTTP header received from client and store these tokens. 
 	* This helps in multiple way :
 		1. To reliably extract the url from the HTTP Header.
 		2. To Validitate the HTTP Header (check its correctness) and generate respective errors.
 		3. Construct a new header in a consistent manner.

III. socket_util.c & socket_util.h 
	* This file is the collection of utility functions which have been used in the proxy.cpp file to DEAL WITH SOCKETS.


SAMPLE TEST
============
~$ telnet localhost 4567
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
GET /~maths/ HTTP/1.0
host: shilloi.iitg.ernet.in
HTTP/1.1 200 OK
Date: Sun, 24 Feb 2013 13:44:02 GMT
Server: Apache/2.2.15 (Red Hat)
X-Powered-By: PHP/5.3.2
Content-Length: 5502
Connection: close
Content-Type: text/html; charset=UTF-8
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Language" content="English" /><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Department of Mathematics, Indian Institute of Technology Guwahati</title>
<link rel="stylesheet" type="text/css" href="default.css" media="screen" />
<link rel="stylesheet" type="text/css" href="csshorizontalmenu.css" />
<script type="text/javascript" src="csshorizontalmenu.js" >
/***********************************************
* CSS Horizontal List Menu- by JavaScript Kit (www.javascriptkit.com)
* Menu interface credits:
* http://www.dynamicdrive.com/style/csslibrary/item/glossy-vertical-menu/
* This notice must stay intact for usage
* Visit JavaScript Kit at http://www.javascriptkit.com/ for this script and 100s more
***********************************************/
</script>
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<a href="http://www.iitg.ernet.in/">Indian Institute of Technology Guwahati</a></h2>
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Last updated: 22 February 2013</div>
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</html>
Connection closed by foreign host.

~$ telnet localhost 4567
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
POST / HTTP/1.0
host: shilloi.iitg.ernet.in
501 Not Implemented
Connection closed by foreign host.