Sending SMS using ASP.NET (C#) through HTTP

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<form id="smsdata" runat="server">
    <asp:Table id="smstable" runat="server" style="text-align:left; border-width:thin;
      border-color:Silver;" BorderStyle="Solid">
        <asp:TableRow>
            <asp:TableCell ColumnSpan="2">
                 <b>Compose a message:</b>
                 <br />
                 <br />
            </asp:TableCell>
        </asp:TableRow>
        <asp:TableRow>
            <asp:TableCell HorizontalAlign="Left" VerticalAlign="Top">
                 <asp:Label ID="labelRecipient" runat="server" Text="Recipient: ">
                 </asp:Label>
            </asp:TableCell>
            <asp:TableCell>
                 <asp:TextBox ID="textboxRecipient" runat="server">
                 </asp:TextBox>
            </asp:TableCell>
        </asp:TableRow>
        <asp:TableRow>
            <asp:TableCell HorizontalAlign="Left" VerticalAlign="Top">
                 <asp:Label ID="labelMessage" runat="server" Text="Message Text: ">
                 </asp:Label>
        </asp:TableCell>
            <asp:TableCell>
                 <asp:TextBox ID="textboxMessage" runat="server" TextMode="MultiLine">
                 </asp:TextBox>
            </asp:TableCell>
        </asp:TableRow>
        <asp:TableRow>
            <asp:TableCell ColumnSpan="2" HorizontalAlign="Center">
                <asp:Button ID="buttonSend" runat="server" Text="Send Message"
                  OnClick="buttonSendOnClick" />
            </asp:TableCell>
        </asp:TableRow>
        <asp:TableRow>
            <asp:TableCell ColumnSpan="2" HorizontalAlign="Center">
                <asp:TextBox ID="textboxError" runat="server" BorderStyle="None"
                  TextMode="MultiLine"></asp:TextBox>
            </asp:TableCell>
        </asp:TableRow>
    </asp:Table>
</form>
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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 = "+441234567";
        textboxMessage.Text = "Hello World!";
    }
}
...
            

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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://127.0.0.1"; //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 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 +
        "&recipient=" + ozRecipients +
        "&messageData=" + ozMessageData;
    ...
}
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protected void buttonSendOnClick(object sender, EventArgs e)
{
...
    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;
    }
}
...