HTTP status code = 0 (iPhone) (objective c) - iphone

Question

I want to ask about the iPhone application objective C problem.
I wrote a program to store the cookies and pass to another URL to retrieve the cookies.
However, I found that one of the return status code is 0. The content of the html is empty.
Can any one help me?
The following is my code.
// create a new mutable url
NSMutableURLRequest *request_get2 = [[[NSMutableURLRequest alloc] init] autorelease];
[request_get2 setURL:[NSURL URLWithString:#"http://www.example.com"]];
[request_get2 setHTTPMethod:#"GET"];
[request_get2 setValue:#"text/html; charset=UTF-8" forHTTPHeaderField:#"Content-Type"];
[request_get2 setValue:#"http://www.example.com" forHTTPHeaderField:#"Referer"];
[request_get2 setHTTPShouldHandleCookies:YES];
// cookiesString is a string, the format is "cookieName=cookieValue;"
[request_get2 setValue: (NSString *) cookiesString forHTTPHeaderField:#"Cookie"];
// doGet - response
NSHTTPURLResponse *response_get2 = nil;
NSError *error_get2 = nil;
NSData *responseData_get2 = [NSURLConnection sendSynchronousRequest:request_get2 returningResponse:&response_get2 error:&error_get2];
NSString *data_get2 = [[NSString alloc]initWithData:responseData_get2 encoding:NSUTF8StringEncoding];
NSString *responseURL_get2 = [[response_get2 URL] absoluteString]; // null value
NSString *responseTextEncodingName_get2 = [response_get2 textEncodingName]; // null value
NSString *responseMIMEType_get2 = [response_get2 MIMEType]; // null value
NSUInteger *responseStatusCode_get2 = [response_get2 statusCode]; //[responseStatusCode intValue]; // the status code is 0
Thank you very much

Answer 1

If you get a 0 for a response code, the response response_get2 probably was never initialized, which might point to a problem with the request unrelated to your web server.
You set error_get2, so check its value after the request is placed:
if (!error_get2) {
NSString *responseURL_get2 = [[response_get2 URL] absoluteString]; // null value
NSString *responseTextEncodingName_get2 = [response_get2 textEncodingName]; // null value
NSString *responseMIMEType_get2 = [response_get2 MIMEType]; // null value
NSUInteger *responseStatusCode_get2 = [response_get2 statusCode]; //[responseStatusCode intValue]; // the status code is 0
}
else {
NSLog(#"something went wrong: %#", [error_get2 userInfo]);
}