Как установить соединение с открытым sip и АТС для отправки сообщений на мобильный номер

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Я использовал этот код и до сих пор не могу правильно установить соединение

protected void Page_Load(object sender, EventArgs e)
{
    textboxRecipient.Width = 400;
    textboxMessage.Width = 450;
    textboxMessage.Rows = 10;
    textboxError.Width = 400;
    textboxError.Rows = 5;

    textboxError.ForeColor = System.Drawing.Color.Red;
    textboxError.Visible = false;
    textboxError.Text = "";

    if (!Page.IsPostBack)
    {
        textboxRecipient.Text = "+917845124339";
        textboxMessage.Text = "Hello World!";
    }

}
protected void buttonSendOnClick(object sender, EventArgs e)
{
    //fields are required to be filled in:
    if (textboxRecipient.Text == "")
    {
        textboxError.Text += "Recipient(s) field must not be empty!\n";
        textboxError.Visible = true;
        return;
    }

    //we are creating the necessary URL string:
    string ozSURL = "http://10.0.0.214"; //where Ozeki NG SMS Gateway is running
    string ozSPort = "9501"; //port number where Ozeki NG SMS Gateway is listening
    string ozUser = HttpUtility.UrlEncode("admin"); //username for successful login
    string ozOriginator = HttpUtility.UrlEncode("+917845124339");//originator of the message

    string ozPassw = HttpUtility.UrlEncode("abc123"); //user's password
    string ozMessageType = "SMS:TEXT"; //type of message
    string ozRecipients = HttpUtility.UrlEncode(textboxRecipient.Text); //who
    //will get the message
    string ozMessageData = HttpUtility.UrlEncode(textboxMessage.Text); //body
    //of message

    string createdURL = ozSURL + ":" + ozSPort + "/httpapi" +
        "?action=sendMessage" +
        "&username=" + ozUser +
        "&password=" + ozPassw +
        "&messageType=" + ozMessageType +
        "&originator=" + ozOriginator +
        "&recipient=" + ozRecipients +
        "&messageData=" + ozMessageData;
    // ...

    try
    {
        //Create the request and send data to Ozeki NG SMS Gateway Server by
      //  HTTP connection
             HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(createdURL);

        //Get response from Ozeki NG SMS Gateway Server and read the answer
        HttpWebResponse myResp = (HttpWebResponse)myReq.GetResponse();
        System.IO.StreamReader respStreamReader = new System.IO.StreamReader(myResp.GetResponseStream());
        string responseString = respStreamReader.ReadToEnd();
        respStreamReader.Close();
        myResp.Close();

        //inform the user
        textboxError.Text = responseString;
        textboxError.Visible = true;
    }
    catch (Exception)
    {
        //if sending request or getting response is not successful, Ozeki NG - SMS Gateway Server may not be running
        textboxError.Text = "Ozeki NG SMS Gateway Server is not running!";
        textboxError.Visible = true;
    }
}

Что я уже пробовал:

Я использовал этот код и до сих пор не могу правильно установить соединение. Мне нужно знать, как на самом деле соединяться шагами.

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