public partial class Chat : Page
{
    public TcpClient client = new TcpClient();
    NetworkStream stream;
    private SslStream ssl;
    private string AppId { get; set; }
    public string AppSecret { get; set; }
    public string AppUrl { get; set; }
    public string UserId { get; set; }
    public string AccessToken { get; set; }
    private string _error = string.Empty;//global error string for watch debugging in VS. 

    public const string FbServer = "chat.facebook.com";
    private const string STREAM_XML = "<stream:stream xmlns:stream=\"http://etherx.jabber.org/streams\" version=\"1.0\" xmlns=\"jabber:client\" to=\"chat.facebook.com\" xml:lang=\"en\" xmlns:xml=\"http://www.w3.org/XML/1998/namespace\">";
    private const string AUTH_XML = "<auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl' mechanism='X-FACEBOOK-PLATFORM'></auth>";
    private const string CLOSE_XML = "</stream:stream>";
    private const string RESOURCE_XML = "<iq type=\"set\" id=\"3\"><bind xmlns=\"urn:ietf:params:xml:ns:xmpp-bind\"><resource>fb_xmpp_script</resource></bind></iq>";
    private const string SESSION_XML = "<iq type=\"set\" id=\"4\" to=\"chat.facebook.com\"><session xmlns=\"urn:ietf:params:xml:ns:xmpp-session\"/></iq>";
    private const string START_TLS = "<starttls xmlns=\"urn:ietf:params:xml:ns:xmpp-tls\"/>";

    protected void Page_Load(object sender, EventArgs e)
this.AppId = "000000082000090";//TODO get from appsettings.
        //AddAdditionalPermissions("xmpp_login");//TODO handle xmpp_login persmission
        this.AppSecret = "d370c1bfec9be6d9accbdf0117f2c495"; //TODO Get appsecret from appsetting.
        this.AppUrl = "https://fbd.anteckna.nu";

        SetUserNameAndAuthToken();

        Connect(FbServer);

        // initiates auth process (using X-FACEBOOK_PLATFORM)
        InitiateAuthProcess(STREAM_XML);

        // starting tls - MANDATORY TO USE OAUTH TOKEN!!!!
        StartTlsConnection(START_TLS);

        // gets decoded challenge from server
        var decoded = GetDecodedChallenge(AUTH_XML);

        // creates the response and signature
        string response = CreateResponse(decoded);

        //send response to server
        SendResponseToServer(response);

        SendMessage("test");

        // finishes auth process
        FinishAuthProcess();

        // we made it!
        string streamresponseEnd = SendWihSsl(CLOSE_XML);

    }
public void Connect(string server)
    {
        try
        {
            client.Connect(server, 5222);
            stream = client.GetStream();
        }
        catch (ArgumentNullException e)
        {
            Console.WriteLine("ArgumentNullException: {0}", e);
        }
        catch (SocketException e)
        {
            Console.WriteLine("SocketException: {0}", e);
        }
    }

private void InitiateAuthProcess(string streamXml)
    {
        string initiation = Send(streamXml);
        if (!initiation.Contains("X-FACEBOOK-PLATFORM"))
            _error = initiation; //TODO handle error
    }
//Facebook answer
//<?xml version='1.0' ?><stream:stream from='chat.facebook.com' id='1' version='1.0' //xmlns:stream='http://etherx.jabber.org/streams' xmlns='jabber:client' xml:lang='en'><stream:features><starttls //xmlns='urn:ietf:params:xml:ns:xmpp-tls'/><mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'><mechanism>X-//FACEBOOK-PLATFORM</mechanism><mechanism>PLAIN</mechanism></mechanisms></stream:features>

public string Send(string dataToSend)
    {
        Byte[] data = Encoding.UTF8.GetBytes(dataToSend);
        stream.Write(data, 0, data.Length);
        data = new Byte[2048];
        Int32 bytes = stream.Read(data, 0, data.Length);
        string responseData = Encoding.UTF8.GetString(data, 0, bytes);

        return responseData;
    }

private void StartTlsConnection(string startTls)
    {
        string tlsResult = Send(startTls);
        if (!tlsResult.ToLower().Contains("proceed"))
            _error = tlsResult; //TODO handle error

        ssl = new SslStream(client.GetStream(), false,
            new RemoteCertificateValidationCallback(ValidateServerCertificate),
            null);
        try
        {
            ssl.AuthenticateAsClient(FbServer, new X509CertificateCollection(), SslProtocols.Tls, false);
        }
        catch (AuthenticationException ex)
        {
            Console.WriteLine("Exception: {0}", ex.Message);
            if (ex.InnerException != null)
            {
                Console.WriteLine("Inner exception: {0}", ex.InnerException.Message);
            }
            Console.WriteLine("Authentication failed - closing the connection.");
            client.Close();
            return;
        }
        string initiationSsl = SendWihSsl(STREAM_XML);
        if (!initiationSsl.Contains("X-FACEBOOK-PLATFORM"))
            _error = initiationSsl;//TODO handle error
    }

//Response from facebook in tlsResult is:
//<proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>

//Response from Facebook in initiationSsl is :
//<?xml version='1.0' ?><stream:stream from='chat.facebook.com' id='1' version='1.0' //xmlns:stream='http://etherx.jabber.org/streams' xmlns='jabber:client' xml:lang='en'><stream:features><mechanisms //xmlns='urn:ietf:params:xml:ns:xmpp-sasl'><mechanism>X-FACEBOOK-PLATFORM</mechanism>
//<mechanism>PLAIN</mechanism></mechanisms></stream:features>


public string SendWihSsl(string dataToSend)
    {
        Byte[] data = System.Text.Encoding.UTF8.GetBytes(dataToSend);

        ssl.Write(data, 0, data.Length);
        ssl.Flush();
        data = new Byte[2048];

        int myBytesRead = 0;
        StringBuilder myResponseAsSB = new StringBuilder();
        do
        {
            myBytesRead = ssl.Read(data, 0, data.Length);
            myResponseAsSB.Append(System.Text.Encoding.UTF8.GetString(data, 0, myBytesRead));
            if (myResponseAsSB.ToString().IndexOf("</") != -1)
            {
                break;
            }
        } while (myBytesRead != 0);

        return myResponseAsSB.ToString();
    }

//reeturn version=1&method=auth.xmpp_login&nonce=234A8DD1234AB6ABSD1234ABC1AB123
private string GetDecodedChallenge(string authXml)
    {
        string sslResponse = SendWihSsl(authXml);

        int start = sslResponse.IndexOf("'>") + 2;
        int end = sslResponse.IndexOf("</");
        string challenge = sslResponse.Substring(start, end - start);
        string decoded = Encoding.UTF8.GetString(Convert.FromBase64String(challenge));
        return decoded;
    }

private void SendResponseToServer(string response)
    {
        string xml = String.Format("<response xmlns=\"urn:ietf:params:xml:ns:xmpp-sasl\">{0}</response>", response);
        string response2 = SendWihSsl2(xml);
        if (!response2.ToLower().Contains("success"))
            _error = response2;
    }

//After 100seconds I get : <success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>