serialPort.DataReceived += new SerialDataReceivedEventHandler(serialPort_DataReceived);

       
void serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            string line;
            int i = 0;
            SerialPort pt = (SerialPort)sender;
            line = pt.ReadExisting();
            //Extract the new message ID's from the returned data string.
            ////+CMGL: 290, "REC READ", "+614030****"
            ////TESTING 1,2,3
            while (line.IndexOf("+CMGL:", i) > 0)
            {
                BubbleMessageEvent("New Message received", EventLogEntryType.Information);
                //Get the line starting with +CMGL
                int startIndex = line.IndexOf("+CMGL:", i);
                //Find the next +GMGL after the last one
                int endIndex = line.IndexOf("+CMGL:", startIndex + 1);
                //if there isn't another +CMGL, then the end of the line is the end of the info
                if (endIndex <= 0) { endIndex = line.Length; }
                //The current message is from the first +CMGL to the next or eof
                string msg = line.Substring(startIndex, endIndex - startIndex);

                //Find the phone number componenet of the message
                string [] msgComponents = msg.Split(',');
                string msgNumber =  msgComponents[2];
                int endNumIndex = msgNumber.IndexOf("\r\n");
                if (endNumIndex <= 0) { endNumIndex = msgNumber.Length; }

                msgNumber = msgNumber.Substring(0,endNumIndex + 1);

                //Find the message componenet of the sms receive notification
                //The message part starts after a new line
                int startMsgIndex = msg.IndexOf("\r\n");
                //The end of the message is before the next new line
                int endMsgIndex = msg.IndexOf("\r\n", startMsgIndex + 1);
                //if there is not a new line then the end of the message is the end of the text
                if (endMsgIndex <= 0) { endMsgIndex = msg.Length; }

                string msgText = msg.Substring(startMsgIndex, endMsgIndex - startMsgIndex);

                ProcessNewMessage(msgText, msgNumber);
                i = startIndex + 1;
            }

        }