Sending a message with file attachment of any type to server in android

Question

I am working on an app which contains message sending module. Users can compose message as in email and send to other users. I want to attach any type of file(.doc .txt image/audio/video) and send to server using

      receiver_id=12345&subject=testapi&msg=testmsg&attach_file=test.txt

I am doing this way

 private void attachFile() {
     Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
    intent.setType("file/*");
    intent.addCategory(Intent.CATEGORY_OPENABLE);

    Intent sIntent = new Intent("com.sec.android.app.myfiles.PICK_DATA");
    sIntent.addCategory(Intent.CATEGORY_DEFAULT);

    Intent chooserIntent;
    if (getPackageManager().resolveActivity(sIntent, 0) != null) {
        // it is device with samsung file manager
        chooserIntent = sIntent;
        chooserIntent.putExtra(Intent.EXTRA_INITIAL_INTENTS,
                new Intent[] { intent });
    } else {
        chooserIntent = intent;
    }

    try {
        startActivityForResult(chooserIntent, PICK_FILE);
    } catch (android.content.ActivityNotFoundException ex) {
        Toast.makeText(getApplicationContext(),
                "No suitable File Manager was found.", Toast.LENGTH_SHORT)
                .show();
    }
}
 public void onActivityResult(int requestCode, int resultCode, Intent data) {
                   if (requestCode == PICK_FILE && resultCode ==getActivity().RESULT_OK) {

                        String FilePath = data.getData().getPath();
                          Log.i("Attachment Path:", FilePath);
                    }
 }

I am getting the file path, but
1) how can I know the file is attached or not/ how to do attachment

2) how to send this file along with the message by specifying filename only (&attach_file=test.txt)?

I have seen many SO questions for sending attachment to email but not like this. Can anyone guide me on this?