Vb.net – Send SMS via Nokia Mobile Using AT Commands

at-commandgsmvb.net

I'm trying to send sms with my Nokia cell phone (C1-01) using AT Commands and I can successfully send SMS with this vb.net code.

Button_Send_Click:

Dim SMSPort = New SerialPort
    With SMSPort
        .PortName = "COM2"
        .BaudRate = 9600
        .Parity = Parity.None
        .DataBits = 8
        .StopBits = StopBits.One
        .Handshake = Handshake.None
        .DtrEnable = True
        .RtsEnable = True
        .NewLine = vbCrLf
    End With

    SMSPort.Open()

    SMSPort.Write("AT+CMGF=1" & vbCrLf)
    Threading.Thread.Sleep(200)

    SMSPort.Write("AT+CMGS=" & Chr(34) & TextBox1.Text & Chr(34) & vbCrLf) 'TextBox1.text = Recipient mobile number and chr(34) = "
    Threading.Thread.Sleep(200)

    SMSPort.Write("TEST MESSAGE" & Chr(26)) 'chr(26) = →
    Threading.Thread.Sleep(200)

    MsgBox(SMSPort.ReadExisting())

    SMSPort.Close()

It's working fine for the 1st time, after fire this code I received SMS on my cell phone TEST MESSAGE(Brilliant) BUT when I press send button in second time I received SMS on my cell phone which contains:
AT+CMGF=1
AT+CMGS=+92XXYYYYYY
TEST MESSAGE

Why in second time it's including "AT Commands i.e AT+CMGF etc.." in SMS?
How can I remove unwanted text from this?
I have also try SMSPort.DiscardInBuffer() and SMSPort.DiscardOutBuffer() Properties after opening and before closing my serial port (SMSPort) but my issue is not resolving.
I have googled alot but all is vain, Please help me to resolve this issue.

Platform: Microsoft Visual Basic 2010 with .NET 2.0

Best Answer

First of all, you must seriously redo your AT command handling to

  • Read and parse the every single response line given back from the modem until you get a final result code. This applies for every single command line invocation, no exceptions whatsoever. See this answer for more details.
  • Never ever call Threading.Thread.Sleep in any code that handles AT commands. See this answer for more details about the risk of aborting the next command.
  • For AT+CMGS specifically you also MUST wait for the "\n\r> " response before sending data, see this answer (again) for more details.

Before fixing these fundamental issues you cannot expect any successful behaviour.

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