A simple proxy server in C#
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  1. #1
    Join Date
    Aug 2012
    Posts
    5

    A simple proxy server in C#

    I have written a simple and minimalist HTTP proxy server that runs on command line. In the Start() method, a TcpListener blocks until it gets a client request and creates a new thread (ThreadHandleClient method) that processes this client, fetches its url and relays data.

    The trouble is in the relay logic that I want to refine. In the first inner loop, I receive all webserver data and send it to client until zero bytes are left. In second inner loop, I do vice-versa: receive all client data and send to web-server until zero bytes left. However, the code gets blocked in the beginning of second inner-loop at client.receive(). This is what I'm basically doing:

    Any help will be truly appreciated. Thanks in advance.

    Code:
    public void Start(IPAddress ip, int port)
        {
        try
        {
        TcpListener listener = new TcpListener(ip, port);
        listener.Start(100);
        while (!stopFlag)
        {
        Socket client = listener.AcceptSocket();
        IPEndPoint rep = (IPEndPoint)client.RemoteEndPoint;
        Thread th = new Thread(ThreadHandleClient);
        th.Start(client);
        }
        listener.Stop();
        }
        catch (Exception ex)
        {
        Debug.Print("START: " + ex.Message);
        }
        }
        public void ThreadHandleClient(object o)
        {
        try
        {
        Socket client = (Socket)o;
        NetworkStream ns = new NetworkStream(client);
        //RECEIVE CLIENT DATA
        byte[] buffer = new byte[2048];
        int rec = 0, sent = 0, transferred = 0, rport = 0;
        string data = "";
        do
        {
        rec = ns.Read(buffer, 0, buffer.Length);
        data += Encoding.ASCII.GetString(buffer, 0, rec);
        } while (rec == buffer.Length);
        //PARSE DESTINATION AND SEND REQUEST
        string line = data.Replace("\r\n", "\n").Split(new string[] { "\n" }, StringSplitOptions.None)[0];
        Uri uri = new Uri(line.Split(new string[] { " " }, StringSplitOptions.None)[1]);
        Debug.Print("CLIENT REQUEST RECEIVED: " + uri.OriginalString);
        if (uri.Scheme == "https")
        {
        rport = 443;
        Debug.Print("HTTPS - 443");
        }
        else
        {
        rport = 80;
        Debug.Print("HTTP - 443");
        }
        IPHostEntry rh = Dns.GetHostEntry(uri.Host);
        Socket webserver = new Socket(rh.AddressList[0].AddressFamily, SocketType.Stream, ProtocolType.IP);
        webserver.Connect(new IPEndPoint(rh.AddressList[0], rport));
        byte[] databytes = Encoding.ASCII.GetBytes(data);
        webserver.Send(databytes, databytes.Length, SocketFlags.None);
        Debug.Print("SENT TO SERVER. WILL NOW RELAY: " + data);
        //START RELAY
        buffer = new byte[2048];
        rec = 0;
        data = "";
        do
        {
        transferred = 0;
        do
        {
        rec = webserver.Receive(buffer, buffer.Length, SocketFlags.None);
        Debug.Print("RECEIVED FROM WEBSERVER[" + rec.ToString() + "]: " + Encoding.ASCII.GetString(buffer, 0, rec));
        sent = client.Send(buffer, rec, SocketFlags.None);
        Debug.Print("SENT TO CLIENT[" + sent.ToString() + "]: " + Encoding.ASCII.GetString(buffer, 0, rec));
        transferred += rec;
        //data += Encoding.ASCII.GetString(serverbytes, 0, rec);
        } while (rec == buffer.Length);
        Debug.Print("loop-1 finished");
        if (transferred == 0)
        break;
        transferred = 0;
        do
        {
        rec = client.Receive(buffer, buffer.Length, SocketFlags.None);
        Debug.Print("RECEIVED FROM CLIENT: " + Encoding.ASCII.GetString(buffer, 0, rec));
        sent = webserver.Send(buffer, rec, SocketFlags.None);
        Debug.Print("SENT TO WEBSERVER[" + sent.ToString() + "]: " + Encoding.ASCII.GetString(buffer, 0, rec));
        transferred += rec;
        } while (rec == buffer.Length);
        Debug.Print("loop-2 finished");
        } while (transferred > 0);
        Debug.Print("LOOP ENDS. EXITING THREAD");
        }
        catch (Exception ex)
        {
        Debug.Print("Error occured: " + ex.Message);
        }

  2. #2
    Join Date
    Nov 2002
    Location
    California
    Posts
    4,553

    Re: A simple proxy server in C#

    Please refrain from double-posting. See my response at http://forums.codeguru.com/showthrea...83#post2080983

    Mike

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