How to set real timeout for NSURLConnection request?

Question

Please look to the following code:

NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:<...> cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:3.0]; 
<...>
[NSURLConnection sendSynchronousRequest:request returningResponse:&WSresponse error:&WSerror]

This code bellow is called from a background thread:

[self performSelectorInBackground:@selector(<...>) withObject:nil];

Sometimes sendSynchronousRequest works much more than 3.0 sec. (abount 1 minute).

1. How to set real timeout instead not working timeoutInterval:3.0?
2. How to add an ability to user to stop freezing NSURLConnection request by Cancel button in any moment?

Thanks a lot for help!

Answer 1

1. Note that in addition to the initializer you called, you can also call -setTimoutInterval: on an NSMutableURLRequest. The timeout value does indeed work, but any value less than 240 is ignored -- that's the minimum value respected by the iOS framework. If you want to set a lower timeout value, then your only choice is to use an asynchronous request.

2. If you want to asynchronously cancel a request (ie, perform the request in the background and allow the foreground UI thread to issue a cancel in response to the user hitting a Cancel or Stop button), then you have to make an asynchronous URL request. There's no way to do it with a synchronous request. For example, you can't even kill a dispatch queue while it is currently executing a block.

You might want to look at ASIHTTPRequest, which wraps up some of this functionality a bit differently.

Answer 2

The timeout interval just describes the amount of time the connection can be idle at any point before it times out. From the Apple documentation:

If during a connection attempt the request remains idle for longer than the timeout interval, the request is considered to have timed out.

So if your data is retrieving any significant amount of data, then it will take longer.

If you want to have more control over how long you wait before you "stop listening" then you should use an asynchronous request. An async request will also make it so the user doesn't see a freeze while waiting?