Ios NSURLSession POST不工作，即使返回200

我试图发布一个字符串并检索服务器的响应，但由于某些原因，它似乎不起作用，我在过去使用过一些类似的代码，它工作得很好。。。 这是我的代码，如果你发现了错误或者有什么建议，请告诉我

NSURL *url = [NSURL URLWithString:@"http://www.NAME.info/test/check.php"];
                    NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
                    sessionConfiguration.HTTPAdditionalHeaders = @{


                                      @"Content-Type"        : @"application/json"
                                                               };
                    NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfiguration];
                    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
                    request.HTTPMethod = @"POST";
                    NSError *error = nil;
                    NSString* str = @"username=test101";
                    NSData* jsonData = [str dataUsingEncoding:NSUTF8StringEncoding];

                    if (!er

ror) {

                    NSURLSessionUploadTask *uploadTask = [session uploadTaskWithRequest:request
                                                                               fromData:jsonData completionHandler:^(NSData *data,NSURLResponse *response,NSError *error) {


                                                                                   NSString *responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
                                                                                   NSString* result2 = [responseString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
                                                                                   NSString *secondString = [result2 stringByReplacingOccurrencesOfString:@" " withString:@""];
                                                                                   NSLog(@"*%@*",secondString);
                                                                                   NSLog(@"RESULT RETURNED%@",response.debugDescription);
                                                                                                                                                                                                                                                                                                       }];

                    [uploadTask resume];
                }

这样做的结果是：

2015-03-26 19:35:03.305 ChannerApp[690:61802] *error_post*
2015-03-26 19:35:03.305 ChannerApp[690:61802] RESULT RETURNED<NSHTTPURLResponse: 0x17023a3a0> { URL: http://www.NAME.info/test/check.php } { status code: 200, headers {
    Connection = "Keep-Alive";
    "Content-Length" = 10;
    "Content-Type" = "text/html; charset=UTF-8";
    Date = "Thu, 26 Mar 2015 17:35:35 GMT";
    "Keep-Alive" = "timeout=5, max=100";
    Server = "Apache/2.4.7 (Ubuntu)";
    "X-Powered-By" = "PHP/5.5.9-1ubuntu4.6";
} }

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如果没有对服务器期望的内容进行描述，则无法回答此问题。服务器日志怎么说？我看到“内容长度”是10。它给了你什么内容？尝试打印原始NSData，然后使用十六进制到文本转换器查看收到的内容。