How to read from Serial (COM) Port? [modified]

[Aghosh Babu]

i want to read data from a serial port(where a gsm modem is connected). I want to read the reply from modem when an AT command is send to the modem. i.e for eg. if i send AT to the modem i want to read the reply OK from the modem! I had used the below codes but the application hangs while executing these lines: string data = Convert.ToString(serialPort1.Read(buffer, 0, (int)buffer.Length)); //read using a Stream string data1 = Convert.ToString(serialPort1.BaseStream.Read(buffer, 0, (int)buffer.Length)); I had also tried string data = serialPort1.ReadLine(); Below is my full code section:

private void button1_Click(object sender, EventArgs e)
{
try
{

            //configuring the serial port
            serialPort1.PortName = "COM6";
            serialPort1.Handshake = Handshake.None;
            serialPort1.BaudRate = 115200;
            serialPort1.DataBits = 8;
            serialPort1.Parity = Parity.None;
            serialPort1.StopBits = StopBits.One;
            serialPort1.DtrEnable = true;

            serialPort1.Open();
            
            string c = "AT+CMGS=";
            string c1 = "\\"+6582083412\\"\\r\\n";
            serialPort1.Write(c+c1);


            string d = "Test message from coded program ";
            //Now send the contents of the message
            serialPort1.Write(d);
            //SerialPortListen();
            char\[\] arr = new char\[1\];

            arr\[0\] = (char)26; //ascii value of Ctrl-Z

            serialPort1.Write(arr, 0, 1);
            
            //string data = Convert.ToString(serialPort1.Read(buffer, 0, (int)buffer.Length));
            //read using a Stream
            //string data1 = Convert.ToString(serialPort1.BaseStream.Read(buffer, 0, (int)buffer.Length));
           //MessageBox.Show(data + " part 2 is : " + data1);

            serialPort1.Close();

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }


    }

I would appreciate your help very much, since this is my first time i am trying to communicate with a serial port. Thanks in advance

modified on Thursday, January 15, 2009 11:48 PM

[lincyang]

use the event DataReceived... this is my email :lebron_y@126.com we can discussion then SerialPort communications. regards

[Bharat Jain]

Hi Aghosh Babu, It seems like you are try to build an application which send SMS using a connect Phone , and the serial port you are using (COM6) is a virtual serial port (port used to connect to through buletooth or USB ) , so please make sure that you com6 is working , by using Apllication like Hyper Terminal (it comes with windows XP) , try to send AT , and recive OK , if its is working over there , than you can try it in your code (dont forget to disconnect hyper terminal bepore try from you code , other wise it will give error , say port already in use). I have used the following code recive data that arrives on serial port

private static void SerialPortDataReceived(object sender, SerialDataReceivedEventArgs e)

{
if (_serialPort.BytesToRead > 0)
{
int bytesToRead = _serialPort.BytesToRead;
byte[] dataRead = new byte[bytesToRead];
string linedata;
_serialPort.Read(dataRead, 0, bytesToRead);
linedata = ConvertToString(dataRead);
}
}

   private string ConvertToString(IEnumerable ByteArray)
    {
        //This Function converts an Byte Array to string , This we 
        // nned to do because if we directly try to read srting ,
        // From the com port , it take Unicode encoding , we need ASCII encoding
        // Hence we need to 
        string tempStringToReturn = string.Empty;
        foreach (byte bt in ByteArray)
        {
            tempStringToReturn = tempStringToReturn + Convert.ToChar(bt);
        }
        return tempStringToReturn;
    }

In the above code SerialPortDataReceived is a event of serial port object , this event is raised when there data arrives on the serial port . Try out with above information , see if it helps , i need to move now , let me know if you find any problem regarding the same

-Regards Bharat Jain bharat.jain.nagpur@gmail.com

[Aghosh Babu]

Hi Bharat, Thanks for the code... i am now able to read data from serial port.. initially i haven't set my handshake property properly...I used serialPort1.ReadExisting(); to read the data from serial port... i think i will redo my code with yours :-D ...i hope your code will automatically initiate the method when a data comes into the port... :-O

[Bharat Jain]

Gr8 to know that the code was helpful.

-Regards Bharat Jain bharat.jain.nagpur@gmail.com