HTTP status code 0 - Error Domain NSURLErrorDomain

Question

I am working on an iOS project      In this application  I am downloading images from the server     Problem     While downloading images I am getting Request Timeout  According to documentation HTTP status code of request timeout is 408     But in my application  I am getting HTTP status code 0 with the following error        Error Domain NSURLErrorDomain Code -1001  The request timed out      UserInfo 0xb9af710     NSErrorFailingURLStringKey http   xxxx com resources p PNG 1383906967 5621 63 jpg     NSErrorFailingURLKey http   xxxx com resources p PNG 1383906967 5621 63 jpg     NSLocalizedDescription The request timed out      NSUnderlyingError 0x13846870  The request timed out         During a search  over internet  I found no information about HTTP Status Code 0      Can anyone explain this to me

User · Answer

Status code  0  can occur because of three reasons 1  The Client cannot connect to the server 2  The Client cannot receive the response within the timeout period 3  The Request was  stopped aborted   by the Client   But these three reasons are not standardized

User · Answer

Sometimes Browser respond to http error handler with Error Object  that have status set to 0  even if you can see 404  401  500 etc  error status in network    This could happen if your Application and API are on different domains - CORS mechanism is applied  According to CORS for each API request browser sends two requests    preflight OPTIONS request to understand if API allows Actual Origin request  when API allows  OPTIOS request respond with status 204 and correct Access-Control-Allow-Origin headers  - browser send next  Actual Origin request     In Application we are handling Error response for  Actual Origin request   and if  preflight OPTIONS request  failed - browser doesn t give correct HttpError object for http error handler  So to get correct status of http response - be sure to get success preflight OPTIONS request response

User · Answer

There is no HTTP status code 0  What you see is a 0 returned by the API library that you are using  You will have to check the documentation for that

User · Answer

CORS in my case     I had such response in a iOS app once  The solution was the missing Access-Control-Allow-Origin    in the headers    More  https   developer mozilla org en-US docs Web HTTP Headers Access-Control-Allow-Origin

User · Answer

The Response was Empty   Most of the case the codes will stats with 1xx  2xx  3xx  4xx  5xx   List of HTTP status codes

User · Answer

A status code of 0 in an NSHTTPURLResponse object generally means there was no response  and can occur for various reasons  The server will never return a status of 0 as this is not a valid HTTP status code   In your case  you are appearing to get a status code of 0 because the request is timing out and 0 is just the default value for the property  The timeout itself could be for various reasons  such as the server simply not responding in time  being blocked by a firewall  or your entire network connection being down  Usually in the case of the latter though the phone is smart enough to know it doesn t have a network connection and will fail immediately  However  it will still fail with an apparent status code of 0   Note that in cases where the status code is 0  the real error is captured in the returned NSError object  not the NSHTTPURLResponse   HTTP status 408 is pretty uncommon in my experience  I ve never encountered one myself  But it is apparently used in cases where the client needs to maintain an active socket connection to the server  and the server is waiting on the client to send more data over the open socket  but it doesn t in a given amount of time and the server ends the connection with a 408 status code  essentially telling the client  you took too long

User · Answer

On gate way timeout  status will be zero on your error call back     error  function  data status headers config       console log status        HTTP status codes

User · Answer

In iOS SDK When your API call time-outs  you get status 0 for that

User · Answer

We got the error   GET http   localhost pathToWebSite somePage aspx raised an http status  0 error   That call is made from windows task that calls a VBS file  so to troubleshoot the problem  pointed a browser to the url and we get a Privacy Error      Your connection is not private      Attackers might be trying to steal your information from localhost    for example  passwords  messages  or credit cards     NET  ERR CERT COMMON NAME INVALID      Automatically report details of possible security incidents to Google    Privacy policy Back to safety This server could not prove that it is   localhost  its security certificate is from   ourdomain com  This may   be caused by a misconfiguration or an attacker intercepting your   connection  Learn more    This is because we have a IIS URL Rewrite rule set to force connections use https  That rule diverts http   localhost to https   localhost but our SSL certificate is based on an outside facing domain name not localhost  thus the error which is reported as status code 0   So a Privacy error could be a very obscure reason for this status code 0   In our case the solution was to add an exception to the rule for localhost and allow http   localhost pathToWebSite somePage aspx to use http   Obscure  yes  but I ll run into this next year and now I ll find my answer in a google search

User · Answer

HTTP response 0 is not standard HTTP response  But it indicates that client could not connect with server and hence forth time out happened

User · Answer

This can happen with a 401 http response if using NSURLConnection   See NSURLConnection returning error instead of response for 401

User · Answer

From my limited experience  I would say that the following two scenario could cause response status code  0  keep in mind  their could be more  but I know of those two    your connection maybe responding slowly  or maybe the the back-end server is not available    the thing is  status  0 is slightly generic  and their could be more use cases that trigger an empty response body

[http] HTTP status code 0 - Error Domain=NSURLErrorDomain?

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