Drupal 7 json ouput error -1 with Java Camunda application

I have made a Drupal module with a single page to display only json data like this :

drupal_add_http_header('Status', $code);
drupal_json_output($data);

$Code can be 200, 204, 401, 404 etc.

When my page is called by Postman it's ok.

When my page is called by Java application it's return -1.

I got the full stack trace and I uploaded it on pastebin : http://pastebin.com/PvCeQuU5

Any idea ?

I set my hook_menu like this :

$items['mymodule/json'] = array(
    'title'             => t('Page title'),
    'page callback'     => array('mymodule_pagejson'),
    'access callback'   => TRUE,
    'type'              => MENU_NORMAL_ITEM,
    'delivery callback' => 'drupal_json_output',
  );
return $items;

Solution

The problem is that the delivery callback with drupal_json_output() returns 4 characters even if it's a 204 status.

But 204 status doesn't allow a Content-Lenght more then 0 (as it's said in the RFC) thus the html data layer of java broke down.

Postman shows that Content-Lenght is more then 0 but allows the query to be executed normally.