title: AT commands Send/receive SMS
body: <p>I am new to AT commands. I am using Nokia E71 to send and receive SMS. I am designing an application for sending SMS, but my code is not working.</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.ComponentModel;
  using System.Data;
  using System.Drawing;
  using System.Linq;
  using System.Text;
  using System.Windows.Forms;
  using System.IO.Ports;
  using System.Threading;
  
  namespace AT_commands
      {
      public partial class Form1 : Form
          {
          SerialPort serialPort;
          public Form1()
              {
              InitializeComponent();
              }
  
          public void Form1_Load(object sender, EventArgs e)
              {
              this.serialPort = new SerialPort();
              this.serialPort.PortName = "COM23";
              this.serialPort.BaudRate = 9600;
              this.serialPort.Parity = Parity.None;
              this.serialPort.DataBits = 8;
              this.serialPort.StopBits = StopBits.One;
              this.serialPort.Handshake = Handshake.RequestToSend;
              this.serialPort.DtrEnable = true;
              this.serialPort.RtsEnable = true;
              this.serialPort.NewLine = System.Environment.NewLine;
              send_sms();
              }
          public bool send_sms()
              {
              label1.Text = "Loaded Successfuly";
              String SMSMessage = "Message to send";
              String CellNumber = "+923333333333";
              String messageToSend = null;
              if (SMSMessage.Length &lt;= 160)
                  {
                  messageToSend = SMSMessage;
                  }
              else
                  {
                  messageToSend = SMSMessage.Substring(0, 160);
                  }
              if (this.IsOpen == true)
                  {
                  this.serialPort.WriteLine(@"AT" + (char)(13));
                  Thread.Sleep(200);
                  this.serialPort.WriteLine("AT+CMGF=1" + (char)(13));
                  Thread.Sleep(200);
                  this.serialPort.WriteLine(@"AT+CMGS=""" + CellNumber + @"""" + (char)(13));
                  Thread.Sleep(200);
                  this.serialPort.WriteLine(SMSMessage + (char)(26));
                  return true;
                  }
              return false;
              }
          public void Open()
              {
              if (this.IsOpen == false)
                  {
                  this.serialPort.Open();
                  }
              }
  
          public void Close()
              {
              if (this.IsOpen == true)
                  {
                  this.serialPort.Close();
                  }
              }
  
          public bool IsOpen
              {
              get
                  {
                  return this.serialPort.IsOpen;
                  }
              }
  
          public void Dispose()
              {
              if (this.IsOpen)
                  this.Close();
              }
          }
      }
  </code></pre>
  
  <p>Please help me with this code!</p>