What is Apache-HttpClient/UNAVAILABLE error (Android, Google App Engine)?

Question

I am confronting myself with a problem that I do not know how to interpret. I am doing a project using Android and Google App Engine. When I am trying to save information in Google App Engine's Big Table, directly from the servlet (hardcoded) - the save is performed with no problem. But when I am trying to save data from my Android device, the save is not performed and the log indicates Apache-HttpClient/UNAVAILABLE error. To be more specific:

405 55ms 0kb Apache-HttpClient/UNAVAILABLE (java 1.4)
82.155.246.249 - - [10/Jun/2013:05:20:59 -0700] "POST /servletnamehere HTTP/1.1"           405 306 - "Apache-HttpClient/UNAVAILABLE (java 1.4)" "appnamehere.appspot.com" ms=56 cpu_ms=21 cpm_usd=0.000034 app_engine_release=1.8.0 instance=00c61b117cede3f754aa1ece730dc88287a20199

I have seen that 405 HTTP error appears in the context of a POST method ( "405 errors often arise with the POST method. You may be trying to introduce some kind of input form on the Web site, but not all ISPs allow the POST method necessary to process the form." ) => indeed, I am trying to perform add (the object is a JPA Entity) in the database using a POST method. The data I am receiving from my Android device is serialized, through an input stream (in my case, working with JSON is not an option, these are the specifications).

Also, 306 HTTP error reffers to switch proxy. While the porevious error might be a bit intuitive, this one is beyond my student knowledge.

I have followed the instructions of this tutorial (http://trumpy.cs.elon.edu/joel/sigcse2011/), which is indeed what I need, but I really cannot figure out what I did wrong. I took again the procedure, stept by step, but I don't see the flaw.

Any help will be indeed appreciated. If I should post some code, I'll gladly do it.

Best wishes, Cropcircles

LATER EDIT:

Now I get 417 HTTP error expectation failed. I have seen that I am supposed to set a certain parameter on false, but this workaround was available only for .NET. Is there anyone who knows what's the correspondent of the following, in Java? I am really really confused.

     <system.net>
      <settings>
       <servicePointManager expect100Continue="false" />
      </settings>
     </system.net>

Solution

This is not an answer, but is too long for a comment and may be helpful, so here goes...

First, it's hard to tell what's going on here because there is limited info. Try to post more of the logging either on the client or on the server. Go to the server console and get more info, for instance, or add debugging in the client. I'd start by trying to make the POST from a debug/testing tool like hurl.it: http://www.hurl.it/ (hurl is a nice web front end to a command line HTTP client named curl, see curl itself if you want a more advanced peek). That way you can test and poke around and make SURE your server side works as you expect with a generic client. Then build other clients (like Android).

Second, "Apache-HttpClient/UNAVAILABLE" is not an error, it's just the user-agent String -- so ignore that part. (UNAVAILABLE is where the version typically is, but some impls don't have access to the version sometimes, it seems.)

Third, the 405 response code IS an error, it means POST is not allowed at the server you are trying to POST to. That can either be because POST is not allowed at all on said server, or you're violating some security policy (such as same origin).

If it's AppEngine, first check the APP you are using and make sure it supports POST (look for info on how to do POST at AppEngine to solve, for instance: google app engine: 405 method not allowed). When you say you can do it directly from a "servlet," do you mean that a POST from a different client works? (Servlet is a server side technology, so that's a little confusing.) If so then make sure your Android app is doing the client part the same way to the same host (multipart vs urlencoded, etc).

For a little more on the security stuff, which could be involved, see this post: Google App Engine + jQuery Ajax = 405 Method Not Allowed.