java.net.ProtocolException: Unexpected status line: HTTP/1.1 422��Unprocessable Entity

Question

I'm making a POST request using Retrofit + Okhttp, and I'm running into the following error:

02-05 04:45:13.981  15972-16249/com.myapp.android D/Retrofit﹕ ---> HTTP POST http://10.0.0.4:3000/api/v1/users/1/posts
02-05 04:45:13.981  15972-16249/com.myapp.android D/Retrofit﹕ Accept: application/json
02-05 04:45:13.981  15972-16249/com.myapp.android D/Retrofit﹕ Content-Type: application/json; charset=UTF-8
02-05 04:45:13.981  15972-16249/com.myapp.android D/Retrofit﹕ Content-Length: 150
02-05 04:45:13.981  15972-16249/com.myapp.android D/Retrofit﹕ {"description":"test","image_url":"https://s3.amazonaws.com/bucket/xxx-4800-b0e0-fc206f95f158.jpeg","title":"test","price":0.0,"user_id":0}
02-05 04:45:13.981  15972-16249/com.myapp.android D/Retrofit﹕ ---> END HTTP (150-byte body)
02-05 04:45:14.001  15972-15972/com.myapp.android W/EGL_genymotion﹕ eglSurfaceAttrib not implemented
02-05 04:45:14.017  15972-16249/com.myapp.android D/Retrofit﹕ ---- ERROR http://10.0.0.4:3000/api/v1/users/1/posts
02-05 04:45:14.017  15972-16249/com.myapp.android D/Retrofit﹕ java.net.ProtocolException: Unexpected status line: HTTP/1.1 422��Unprocessable Entity
            at com.squareup.okhttp.internal.http.StatusLine.parse(StatusLine.java:73)
            at com.squareup.okhttp.internal.http.HttpConnection.readResponse(HttpConnection.java:187)
            at com.squareup.okhttp.internal.http.HttpTransport.readResponseHeaders(HttpTransport.java:80)
            at com.squareup.okhttp.internal.http.HttpEngine.readNetworkResponse(HttpEngine.java:791)
            at com.squareup.okhttp.internal.http.HttpEngine.access$200(HttpEngine.java:90)
            at com.squareup.okhttp.internal.http.HttpEngine$NetworkInterceptorChain.proceed(HttpEngine.java:784)
            at com.squareup.okhttp.internal.http.HttpEngine.readResponse(HttpEngine.java:645)
            at com.squareup.okhttp.Call.getResponse(Call.java:263)
            at com.squareup.okhttp.Call$ApplicationInterceptorChain.proceed(Call.java:219)
            at com.squareup.okhttp.Call.getResponseWithInterceptorChain(Call.java:192)
            at com.squareup.okhttp.Call.execute(Call.java:79)
            at retrofit.client.OkClient.execute(OkClient.java:53)
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:326)
            at retrofit.RestAdapter$RestHandler.access$100(RestAdapter.java:220)
            at retrofit.RestAdapter$RestHandler$1.invoke(RestAdapter.java:265)
            at retrofit.RxSupport$2.run(RxSupport.java:55)
            at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:422)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at retrofit.Platform$Android$2$1.run(Platform.java:142)
            at java.lang.Thread.run(Thread.java:841)
02-05 04:45:14.017  15972-16249/com.myapp.android D/Retrofit﹕ ---- END ERROR

Using the following libs:

compile 'com.squareup.retrofit:retrofit:1.9.0'
compile 'com.squareup.okhttp:okhttp-urlconnection:2.2.0'
compile 'com.squareup.okhttp:okhttp:2.2.0'

I'm expecting something like the following to come back (intentionally testing a 422 error):

{
    "title": [
        "is too short (minimum is 6 characters)"
    ]
}

I get the expected result when sending via Postman (https://chrome.google.com/webstore/detail/postman-rest-client/fdmmgilgnpjigdojojpjoooidkmcomcm?hl=en)

Edit: I'm making the following call in Rails to return this 422 result:

render json: @post.errors.to_json, status: :unprocessable_entity

Another Edit:

Here's a screenshot of the request being made via Wireshark. Nothing looks out of the ordinary, but I've also never used the tool before.

Here's the appropriate hex.

Answer 1

Your server appears to violate the HTTP spec. The status line is defined as follows:

The first line of a response message is the status-line, consisting of the protocol version, a space (SP), the status code, another space, a possibly empty textual phrase describing the status code, and ending with CRLF.

status-line = HTTP-version SP status-code SP reason-phrase CRLF

From the exception it appears that a non-space character (or two) is between the status code and reason phrase.

OkHttp is looking for ASCII spaces (character #32) between these elements. You can use something like WireShark or maybe Charles to intercept the network traffic and figure out what characters are being used by your HTTP server.