大小为1的整数或字符串是必需的异常

Question

我正在尝试使用HttpURLConnection在网上找到无线连接到我的Raspberry pi的草图程序..它正在捕获异常“需要一个整数或大小为1的字符串”而且我不知道错误在哪里。当用户点击UI上的按钮到Raspberry pi上运行的网络服务器时，程序基本上会发送一个字符或数字。这是send命令的一部分：

private void sendCommand(String command) {
    final String cmd = command;

    AsyncTask task = new AsyncTask() {

        private String resp;

        @Override
        protected Object doInBackground(Object... params) {
            try {
                resp = Sender.getStringResponseFromGetRequest(
                        "http://192.168.1.111:8888/" + cmd);
            } catch (IOException e) {
                resp = e.getMessage();
            }
            return null;
        }

    };
}
        @Override
        protected void onPostExecute(Object result) {
            if(!resp.equals("OK")){
                Toast.makeText(ctx, resp, Toast.LENGTH_LONG).show();
            }
            super.onPostExecute(result);
        }
    };

    task.execute();
}

}

这里是getStringResponse ..方法：

public static String getStringResponseFromGetRequest(String requestUrl)
        throws IOException {
    URL url1;
    URLConnection urlConnection;
    DataInputStream inStream;

    url1 = new URL(requestUrl);
    urlConnection = url1.openConnection();
    ((HttpURLConnection) urlConnection).setRequestMethod("GET");
    urlConnection.setDoInput(true);
    urlConnection.setDoOutput(false);
    urlConnection.setUseCaches(false);

    inStream = new DataInputStream(urlConnection.getInputStream());

    return inStream.readLine();
}