C#中的串行端口信号读取，接收到错误的数据

一个micro向我发送一个10位帧，其中第一位是Startbit，最后一位也是Stopbit。我使用了以下程序来获取数据，但数据是假的；例如当它向我发送21时，我接收33。出了什么问题？

class Program
    {
        static void Main(string[] args)
        {
            dataCollector dc = new dataCollector();
            dc.Start("COM23");
        }    
    public class dataCollector : IDisposable
    {    
        private static dataCollector collector;
        public dataCollector()
        {
            thread = new Thread(new ThreadStart(ThreadMain));
        }
        private Thread thread;
        private SerialPort port;
        private void ThreadMain()
        {
            try
            {
                if (port.IsOpen)
                    throw new Exception();
            }
            catch (Exception)
            {
                Console.Out.WriteLine("port is not open!!");
            }
            while (port.IsOpen)
            {
                try
                {
                    var b = port.ReadByte();
                    Console.Out.WriteLine(b);
                    //System.Threading.Thread.Sleep(2000);
                }
                catch (Exception) { }
            }
        }
        public void Start(string portName, int rate=2600)
        {
                port = new SerialPort("COM23");//baudrate is 2600;
                port.BaudRate = 9600; 
                //port.DataBits = 8;
                //port.StopBits = StopBits.One;
                //port.Parity = Parity.None;
                port.Open();
            thread.Start();
        }
        public void Stop()
        {
            if (port != null)
            {
                if (port.IsOpen) port.Close();
                if (thread.IsAlive) thread.Join();
                port.Dispose();
            }
        }
        public void Dispose()
        {
            Stop();
        }
    }