How to create a simple proxy in Managed C++

Introduction

Many people have been asking me about a how to create a proxy. Actually is very simple to do in Managed C++. This article is made very simple, you can add as much as you want at the base class we can call it CHttpProxy

I'll be using the known class  TcpClient.

// Header File

// CHttpProxy.h 

__gc class CHttpProxy 
{ 
public: 
    CHttpProxy(String __gc *szHost, int port); 
    String __gc *m_host; 
    int m_port; 
    unsigned char SendToServer(unsigned char Packet __gc[]) __gc[]; 
};

// CHttpProxy.cpp

#using <mscorlib.dll>
#using <SYSTEM.DLL>
using namespace System;
using System::Net::Sockets::TcpClient;
using System::String;
using System::Exception;
using System::Net::Sockets::NetworkStream;
#include "httpproxy.h"


#include <stdio.h>


CHttpProxy::CHttpProxy(String __gc *szHost, int port)
{
    m_host = szHost;
    m_port = port;
    
}

unsigned char CHttpProxy::SendToServer(unsigned char    Packet __gc[]) __gc[]
{
    TcpClient * tcpclnt = new TcpClient();
    unsigned char bytes __gc[];  

    try
    {
        tcpclnt->Connect(m_host,m_port); 
    }

    catch (Exception  * e )
    {
        Console::WriteLine(e->ToString());
          return NULL;
    }

    // Send it

    if ( tcpclnt )
    {
        NetworkStream * networkStream =  tcpclnt->GetStream();

        int size = Packet->get_Length();        
        networkStream->Write(Packet, 0, size);

        bytes = new unsigned char __gc[tcpclnt->ReceiveBufferSize];
    
        networkStream->Read(bytes, 0, (int) tcpclnt->ReceiveBufferSize);

        return (bytes);
    }

    return (NULL);
}

Simple isn't it? This class creates a connection to the "real" IIS server.

So(...) How to use it now? Simpler than bowling water, you may remember this part of the code from my previous article:

TcpListener * pTcpListener;
TcpListener = new TcpListener(80);
TcpListener->Start(); 
TcpClient * pTcpClient; 
unsigned char  sendbytes __gc[];
pTcpClient = m_TcpListener->AcceptTcpClient();
NetworkStream * networkStream = pTcpClient->GetStream();
bytes = new unsigned char __gc[tcpCl->ReceiveBufferSize];
networkStream->Read(bytes, 0, (int) tcpCl->ReceiveBufferSize);

// Now we got the request

Console::WriteLine(S"Packet Received");            
CHttpProxy    *pProxy; 
pProxy    = new CHttpProxy(S"www.codeproject.com", 80);    // Goes somewhere else!

sendbytes = pProxy->SendToServer(bytes);
networkStream->Write(sendbytes, 0 , sendbytes->get_Length());
networkStream->Close();

We listen on port 80 for any connection. Anything that comes in that port is re-directed to www.codeproject.com It's actually a pretty easy concept. The most interesting part comes when you get the buffer. You got the control to remove images from the HTML or change the content on the fly.

In my next article will look into those possibilities.