title: BasicNetwork.performRequest: Unexpected response code 503
body: <p><strong>Android Volley POST method error</strong> </p>
  
  <p>BasicNetwork.performRequest: <strong>Unexpected response code 503</strong></p>
  
  <p>Post request send to the server.</p>
  
  <pre><code>Map&lt;String, String&gt; jsonParams = new HashMap&lt;String, String&gt;();
  
  jsonParams.put("LoginForm[email]",email);
  jsonParams.put("LoginForm[password]",password);
  jsonParams.put("TOKEN", token);
  
  JsonObjectRequest postRequest = new JsonObjectRequest( Request.Method.POST, URL,
          new JSONObject(jsonParams),
          new Response.Listener&lt;JSONObject&gt;() {
              @Override
              public void onResponse(JSONObject response) {
                  // on Response
              }
          },
          new Response.ErrorListener() {
              @Override
              public void onErrorResponse(VolleyError error) {
                  // on Error Response
              }
          }) {
      @Override
      public Map&lt;String, String&gt; getHeaders() throws AuthFailureError {
          HashMap&lt;String, String&gt; headers = new HashMap&lt;String, String&gt;();
          headers.put("Content-Type", "application/json; charset=utf-8");
          headers.put("User-agent", System.getProperty("http.agent"));
          return headers;
      }
  };
  RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
  requestQueue.add(postRequest);
  </code></pre>