Serial port JNI

Hello there

so I am trying to translate this SerialPortClass

http://android-serialport-api.googlecode.com/svn-history/r4/trunk/project/src/android/serialport/SerialPort.java

which uses JNI but I really cant get the grasp of how to correctly translate the bottom part

the lines

// JNI private native static FileDescriptor open(String path, int baudrate, int flags); public native void close(); static { System.loadLibrary("serial_port"); }

heres my port so far

public class SerialPort {

    private static string TAG = "SerialPort";

    private FileDescriptor mFd;
    private FileInputStream mFileInputStream;
    private FileOutputStream mFileOutputStream;

    public SerialPort(File device, int baudrate, int flags)
    {

    /* Check access permission */
    if (!device.CanRead() || !device.CanWrite()) {

        try 
        {
            Log.Debug(TAG, "1============================");

            // Missing read/write permission, trying to chmod the file 
            Process su;
            su = Runtime.GetRuntime().Exec("/system/xbin/su");


            //String cmd = "chmod 666 " + device.getAbsolutePath() + "\n"
                    //+ "exit\n";
            String cmd = "chmod 666 " + device.AbsolutePath;
            Log.Debug(TAG, "cmd=====================" + cmd);
            Runtime.GetRuntime().Exec(cmd);


            //su.getOutputStream().write(cmd.getBytes());
            if (/*(su.waitFor() != 0) || */!device.CanRead() || !device.CanWrite()) 
            {
                Log.Debug(TAG, "2=====================");
                throw new SecurityException();
            }
        } 
        catch (Exception ex) 
        {
            Log.Debug(TAG, "3=================");
            Log.Debug(TAG, ex.Message);
            throw new SecurityException();
        }

        //do_exec("su root\n");
        //Log.e(TAG, "=============cmd : "+device.getAbsolutePath());
        //do_exec("chmod 755 " + device.getAbsolutePath() + "\n");
        //do_exec("rm /sdcard/123");
    //Runtime.getRuntime().exec("/system/xbin/su");
    //Runtime.getRuntime().exec("chmod 755 /dev/ttyS1");

    }

        try
        {
            mFd = open(device.AbsolutePath, baudrate, flags);
            if (mFd == null)
            {
                Log.Debug(TAG, "native open returns null");
                throw new IOException();
            }
            mFileInputStream = new FileInputStream(mFd);
            mFileOutputStream = new FileOutputStream(mFd);
        }
        catch (Exception ex)
        {

        }


}

    public InputStream getInputStream()
    {
        return mFileInputStream;
    }

    public OutputStream getOutputStream()
    {
        return mFileOutputStream;
    }

    [DllImport("serial_port")]
    private extern static FileDescriptor open(string path, int baudrate, int flags);

    [DllImport("serial_port")]
    public extern static void close();



}

I probably have the DLLImport name wrong thanks in advance :D