I was getting this error as well, but on actual devices rather than the simulator. We noticed the error when accessing our heroku backend on HTTPS (gunicorn server), and doing POSTS with large bodys (anything over 64Kb). We use HTTP Basic Auth for authentication, and noticed the error was resolved by NOT using the didReceiveChallenge: delegate method on NSURLSession, but rather baking in the Authentication into the original request header via adding Authentiation: Basic <Base64Encoded UserName:Password>. This prevents the necessary 401 to trigger the didReceiveChallenge: delegate message, and the subsequent network connection lost.

我们有这个确切的错误，它原来是NSURLRequest的底层HTTP实现的问题:

据我们所知，当iOS 8/9/10/11接收到一个带有keep - alive头的HTTP响应时，它会保留这个连接以供以后重用(这是应该的)，但它会保留它的时间超过keep - alive头的超时参数(它似乎总是保持连接活跃30秒)。 然后，当应用程序在不到30秒后发送第二个请求时，它会尝试重新使用可能已经被服务器丢弃的连接(如果超过了真正的Keep-Alive时间)。

以下是我们目前找到的解决方案:

Increase the timeout parameter of the server above 30 seconds. It looks like iOS is always behaving as if the server will keep the connection open for 30 seconds regardless of the value provided in the Keep-Alive header. (This can be done for Apache by setting the KeepAliveTimeout option. You can simply disable the keep alive mechanism for iOS clients based on the User-Agent of your app (e.g. for Apache: BrowserMatch "iOS 8\." nokeepalive in the mod file setenvif.conf) If you don't have access to the server, you can try sending your requests with a Connection: close header: this will tell the server to drop the connection immediately and to respond without any keep alive headers. BUT at the moment, NSURLSession seems to override the Connection header when the requests are sent (we didn't test this solution extensively as we can tweak the Apache configuration)

打开Charles为我解决了这个问题，这看起来很奇怪……

Charles是一个HTTP代理/ HTTP监视器/反向代理，使开发人员能够查看他们的机器和Internet之间的所有HTTP和SSL / HTTPS流量。这包括请求、响应和HTTP报头(其中包含cookie和缓存信息)。

我通过VPN连接。去使能VPN解决了问题。

参见pjebs 1月5日在Github上的评论。

Method1:

if (error.code == -1005)
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{

        dispatch_group_t downloadGroup = dispatch_group_create();
        dispatch_group_enter(downloadGroup);
        dispatch_group_wait(downloadGroup, dispatch_time(DISPATCH_TIME_NOW, 5000000000)); // Wait 5 seconds before trying again.
        dispatch_group_leave(downloadGroup);
        dispatch_async(dispatch_get_main_queue(), ^{
            //Main Queue stuff here
            [self redoRequest]; //Redo the function that made the Request.
        });
    });

    return;
}

也有人建议重新连接该网站，

即触发POST请求两次

解决方法:使用一个方法做连接到站点，返回(id)，如果网络连接丢失，返回使用相同的方法。

方法2

-(id) connectionSitePost:(NSString *) postSender Url:(NSString *) URL {
     // here set NSMutableURLRequest =>  Request

    NSHTTPURLResponse *UrlResponse = nil;
    NSData *ResponseData = [[NSData alloc] init];

    ResponseData = [NSURLConnection sendSynchronousRequest:Request returningResponse:&UrlResponse error:&ErrorReturn];

     if ([UrlResponse statusCode] != 200) {

          if ([UrlResponse statusCode] == 0) {

                  /**** here re-use method ****/
                  return [self connectionSitePost: postSender Url: URL];
          }

     } else {
          return ResponseData;
     }

}

我也有同样的问题。解决方案很简单，我已经设置HTTPBody，但还没有设置HTTPMethod POST。修好之后，一切都好了。