这和AFNetworking没有关系，code=-1012 是系统提供 NSURLError 的错误信息。这有对照表http://blog.csdn.net/yesjava/article/details/8056681。
NSURLErrorUserCancelledAuthentication = -1012。用户取消验证。
搜搜就知道原因了。

1.无线访问和蜂窝访问的DNS服务器不一样. 看报错信息,你访问的服务器开启了SSL,使用了自生成的证书.
2.AFNetworking 2.x 我没有遇到过类似问题，在3.x版本下:
2.1 代码修改：

//使用默认的security policy, 注释掉类似代码：
//sessionMgr.securityPolicy = [AFSecurityPolicy policyWithPinningMode:AFSSLPinningModeNone];
//以下和AFNetworking 2.x相同
sessionMgr.securityPolicy.allowInvalidCertificates = YES;
//以下是AFNetworking 3.x 下需要的
sessionMgr.securityPolicy.validatesDomainName = NO;

2.2 Info.plist 加入ATS：

<key>NSAppTransportSecurity</key>
<dict>
    <key>NSAllowsArbitraryLoads</key>
    <true/>
</dict>

3.代码举例：

//#自生成证书

-(IBAction)clickOnSSLWithJSON:(id)sender {
    NSLog(@"ssl with json");
    
    NSURL *url = [NSURL URLWithString:@"https://192.168.1.6:3000"];
    AFHTTPSessionManager *sessionMgr=[[AFHTTPSessionManager alloc]initWithBaseURL:url];
    sessionMgr.responseSerializer = [AFHTTPResponseSerializer serializer];
 
    sessionMgr.responseSerializer.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"text/html",nil];
    //in this case, Info.plist should be added with keys 'NSAppTransportPolicy' and 'NSAllowsArbitraryLoads',
    //and security policy  should be used with default.
    //following setting is same as AFNetworking 2.x
    sessionMgr.securityPolicy.allowInvalidCertificates = YES;
    //following setting is specified for AFNetworking 3.x
    sessionMgr.securityPolicy.validatesDomainName = NO;
    [sessionMgr GET:@"" parameters:nil progress:nil
            success: ^(NSURLSessionDataTask * _Nonnull task, id _Nullable result){
                //NSUTF8StringEncoding should be encoded for response data.
                NSLog(@"ok:\n%@",[[NSString alloc]initWithData:result encoding:NSUTF8StringEncoding]);
            }
            failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error)
            {
                NSLog(@"error:\n%@",error);
            }];
}