如果有人在将文件上载到后端服务器时得到此错误，请确保接收服务器具有您的媒体允许的最大内容大小。在我的例子中，NGINX需要一个更高的client_max_body_size。NGINX会在上传完成之前拒绝请求，这样就不会返回错误代码。

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)

我的问题在服务器上。我正在使用Python的BaseHTTPRequestHandler类，我没有在响应中发送正文。当我像下面这样放一个空身体时，我的问题就解决了。

def do_POST(self):
    content_len = int(self.headers.get('Content-Length'))
    post_body = self.rfile.read(content_len)
    msg_string = post_body.decode("utf-8")
    msg_json = json.loads(msg_string)
    self.send_response(200)
    self.end_headers() #this and the following lines were missing
    self.wfile.write(b'') 

当传递一个NSURLRequest到一个NSURLSession而没有设置请求的HTTPMethod时，我击中了这个错误。

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:urlComponents.URL];

ErrorDomain =NSURLErrorDomain Code=-1005 "The network connection was lost."

不过，添加HTTPMethod，连接就可以正常工作了

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:urlComponents.URL];
[request setHTTPMethod:@"PUT"];

我也有同样的问题，问题是Alomofire和NSUrlSession的bug。当你从safari或电子邮件返回到应用程序时，你需要等待近2秒才能通过Alamofire进行网络响应

 DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
       Your network response
}

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。