在c#中写入linux tty (/dev/)文件

我需要我的程序执行一个命令，在Bash中看起来像这样:echo P1-12=175>/dev/servoblaster"。如何在Linux上的Mono/c#中做到这一点?我写了下面的类:

public static class ServoBlasterPWM
{
    private static FileStream devFile;
    public static bool IsRunning
    {
        get;
        private set;
    }
    public static bool Initialize()
    {
        try
        {
            devFile = File.Open("/dev/servoblaster", FileMode.Open);
        }
        catch (Exception e)
        {
            Log.Error("Error while setting up port for Servo Blaster: " + e.Message);
            return false;
        }
        Log.Success("ServoBlaster is set up.");
        IsRunning = true;
        return true;
    }
    public static void SetPWMOutput(int pin, int valueSteps)
    {
        //byte[] bytes = Encoding.ASCII.GetBytes("P1-" + pin.ToString() + "=" + valueSteps.ToString());
        byte[] bytes = Encoding.ASCII.GetBytes("P1-12=175");
        devFile.Write(bytes, 0, bytes.Length);
        devFile.Flush();
        Console.WriteLine("Wrote to file");
    }
    public static void Shutdown()
    {
        devFile.Close();
        IsRunning = false;
        Log.Info("Servo Blaster has been shut down.");
    }
}

这段代码不起作用。我也尝试过StreamWriter而不是FileStream，但是它崩溃了，出现了一个异常，说流不支持查找。我不知道该怎么做。请帮助。

byte[] bytes = ASCIIEncoding.UTF8.GetBytes("P1-12=175") ;

byte[] bytes = ASCIIEncoding.Default.GetBytes("P1-12=175") ;