When I send a JSON object to the server via a POST request, the server returns an error message.

Code:

```
public String sendStuff(String reqUrl,String arg1, String arg2){
    String response;
    try{
        URL url = new URL(reqUrl);
        HttpURLConnection conn = (HttpURLConnection)url.openConnection();
        conn.setDoOutput(true);
        conn.setDoInput(true);
        conn.setRequestMethod("POST");
        JSONObject jsonObject = new JSONObject();
        jsonObject.accumulate("argument1",arg1);
        jsonObject.accumulate("argument2",arg2);
        String json = jsonObject.toString();
        DataOutputStream out = new DataOutputStream(conn.getOutputStream());
        out.writeBytes(URLEncoder.encode(json,"UTF-8"));
        out.flush();
        out.close();

        int HttpResult = conn.getResponseCode();
        if(HttpResult == HttpURLConnection.HTTP_OK){
            response = convertStreamToString(conn.getInputStream());
            return response;
        }
    }catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

private String convertStreamToString(InputStream is) {
    BufferedReader reader = new BufferedReader(new InputStreamReader(is));
    StringBuilder sb = new StringBuilder();

    String line;
    try {
        while ((line = reader.readLine()) != null) {
            sb.append(line).append('\n');
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return sb.toString();
}

```

Error message:

> 
> {"ERROR":"A JSONObject text must begin with '{' at 1 [character 2 line 1]"}
> 
> 
> 

According to the RESTful service, this error message would only be returned if the JSON is malformed. I've tested the service manually by a Chrome extension and it works fine with that.

I think there shouldn't be an error since I'm directly converting the JSON to a string by a method from the `org.json` package.

I searched for a solution, but couldn't find one.