The certificate for this server is invalid.

具体错误信息如下：

Error Domain=NSURLErrorDomain Code=-1202 "The certificate for this server is invalid. You might be connecting to a server that is pretending to be “222.111.000.1” which could put your confidential information at risk."

如果用NSURLSession进行https网络请求，出现上述错误。表明，请求服务器的证书不符合ATS要求，需要实现NSURLSessionDelegate的代理方法，在检测服务器证书是否有效时，过滤掉该服务器。

初始化NSURLSession时，

NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc]init]];

实现代理方法，即可。

-(void)URLSession:(NSURLSession *)session didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition, NSURLCredential * _Nullable))completionHandler {
    
    NSURLSessionAuthChallengeDisposition disposition = NSURLSessionAuthChallengePerformDefaultHandling;
    __block NSURLCredential *credential = nil;
    
    if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
        credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
        if (credential) {
            disposition = NSURLSessionAuthChallengeUseCredential;
        } else {
            disposition = NSURLSessionAuthChallengePerformDefaultHandling;
        }
    } else {
        disposition = NSURLSessionAuthChallengePerformDefaultHandling;
    }
    
    if (completionHandler) {
        completionHandler(disposition, credential);
    }
}

备注：

应用中若使用http请求，需要在Info.plist文件中加如下参数：

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