I have seen http://www.vbdotnetheaven.com/Code/Aug2003/2146.asp - but it
does not work.

I need a working example....if anyone has seen one.

Jim

Sorry for my ignorance, but what does a  proxy server do exactly?  I am not
familiar with the term "Proxy".  Thanks for any info or links that you can
share.
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A proxy server makes requests on behalf of another machine (PC).  Proxy
servers are mostly used for HTTP traffic, but can be used for any traffic
that needs a "go-between" for 2 PCs (like the servers that relay IM
conversations between PCs).

When a proxy is used for HTTP traffic, you must point your browser to the
proxy instead of to your cable modem, router or direct internet connection.
The proxy becomes the target of your HTTP requests.  The proxy then connects
to the network (or internet) on your behalf, retrieves your requested
page/resource and passes it along to you.

Proxies can be used to filter out ads, pop-ups, viruses, adult content,
objectionable websites, allow anonymous web surfing (see www.anonymizer.com
for an example of this), etc..  They can also be used to track employee web
usage (a big brother kind of thing that I, personally, oppose).

For a better explanation, see http://en.wikipedia.org/wiki/Proxy_server .

Hope this helps.

Jim

Jim, thanks a lot for taking the time to educate me on proxies.  This was an
excellent description.
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I have found an example of VB.Net console proxy, and have fixed a couple of
errors.  But, it does not seem to pass through pictures and throws an error
that says "An existing connection was forcibly closed by the remote host".

The goal is to be able to filter the content on the way to the browser.  Any
help you could give with this project would be appreciated.

The VB.Net 2005 code is as follows......


Imports System '
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports System.IO
Imports System.Threading

Namespace WebProxy2

    Class WebProxy2
        Private clientSocket As Socket
        Private read() As [Byte] = New Byte(1024) {}
        Private Buffer As [Byte]() = Nothing
        Private ASCII As Encoding = Encoding.ASCII
        Private HTTP_VERSION As String = "HTTP/1.0"
        Private CRLF As String = ControlChars.Cr + ControlChars.Lf
        Private RecvBytes(4096) As [Byte]


        Public Sub New(ByVal socket As Socket)
            Me.clientSocket = socket
        End Sub 'New

        Public Sub run()
            Dim clientmessage As [String] = " "
            Dim sURL As [String] = " "
            Dim bytes As Integer = readmessage(read, clientSocket,
clientmessage)
            If bytes = 0 Then
                Return
            End If
            Dim index1 As Integer = clientmessage.IndexOf(" "c)
            Dim index2 As Integer = clientmessage.IndexOf(" "c, index1 + 1)
            If index1 = -1 Or index2 = -1 Then
                Throw New IOException()
            End If
            Console.WriteLine("Connecting to Site: {0}",
clientmessage.Substring(index1 + 1, index2 - index1))
            Console.WriteLine("Connection from {0}",
clientSocket.RemoteEndPoint)

            Dim part1 As String = clientmessage.Substring(index1 + 1,
index2 - index1)
            Dim index3 As Integer = part1.IndexOf("/"c, index1 + 8)
            Dim index4 As Integer = part1.IndexOf(" "c, index1 + 8)
            Dim index5 As Integer = index4 - index3
            sURL = part1.Substring(index1 + 4, part1.Length - index5 - 8)

            Try
                Dim IPHost As IPHostEntry = Dns.Resolve(sURL)
                Console.WriteLine("Request resolved: ", IPHost.HostName)
                Dim aliases As String() = IPHost.Aliases
                Dim address As IPAddress() = IPHost.AddressList
                Console.WriteLine(address(0))
                Dim sEndpoint As New IPEndPoint(address(0), 80)
                Dim IPsocket As New Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp)
                IPsocket.Connect(sEndpoint)
                If IPsocket.Connected Then
                    Console.WriteLine("Socket connect OK")
                End If
                Dim [GET] As String = clientmessage
                Dim ByteGet As [Byte]() = ASCII.GetBytes([GET])
                IPsocket.Send(ByteGet, ByteGet.Length, 0)
                Dim rBytes As Int32 = IPsocket.Receive(RecvBytes,
RecvBytes.Length, 0)
                Console.WriteLine("Recieved {0}", +rBytes)
                'Buffer = RecvBytes;
                Dim strRetPage As [String] = Nothing
                strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0,
rBytes)
                While rBytes > 0
                    rBytes = IPsocket.Receive(RecvBytes, RecvBytes.Length,
0)
                    strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0,
rBytes)
                End While
                IPsocket.Shutdown(SocketShutdown.Both)
                IPsocket.Close()
                sendmessage(clientSocket, strRetPage)
            Catch exc2 As Exception
                Console.WriteLine(exc2.ToString())
            End Try
        End Sub 'run

        Private Function readmessage(ByVal ByteArray() As Byte, ByRef s As
Socket, ByRef clientmessage As [String]) As Integer
            Dim bytes As Integer = s.Receive(ByteArray, 1024, 0)
            Dim messagefromclient As String =
Encoding.ASCII.GetString(ByteArray)
            clientmessage = CType(messagefromclient, [String])
            Return bytes
        End Function 'readmessage


        Private Sub sendmessage(ByVal s As Socket, ByVal message As String)
            Buffer = New [Byte](message.Length + 1) {}
            Dim length As Integer = ASCII.GetBytes(message, 0,
message.Length, Buffer, 0)
            s.Send(Buffer, length, 0)
        End Sub 'sendmessage

        'Entry point which delegates to C-style main Private Function
        Public Overloads Shared Sub Main()
            Main2(System.Environment.GetCommandLineArgs())
        End Sub


        Overloads Shared Sub Main2(ByVal args() As String)
            Const port As Integer = 8889

            'must set up local byte array for address type
            Dim myIP(3) As Byte
            myIP(0) = 127
            myIP(1) = 0
            myIP(2) = 0
            myIP(3) = 1
            Dim myLocalAddress As New System.Net.IPAddress(myIP)

            'use byte array to open a listner
            Dim tcplistener1 As New TcpListener(myLocalAddress, port)
'TcpListener(port)

            Console.WriteLine("Listening on port {0}", +port)
            tcplistener1.Start()
            While True
                Dim socket As Socket = tcplistener1.AcceptSocket()
                Dim webproxy As New WebProxy2(socket)
                Dim thread As New Thread(New ThreadStart(AddressOf
webproxy.run))
                thread.Start()
            End While
        End Sub 'Main
    End Class 'WebProxy2
End Namespace 'WebProxy2

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