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Answer : An established connection was aborted by the software in your host machine That is a boiler-plate error message, it comes out of Windows. The underlying error code is WSAECONNABORTED. Which really doesn't mean more than "connection was aborted". You have to be a bit careful about the "your host machine" part of the phrase. In the vast majority of Windows application programs, it is indeed the host that the desktop app is connected to that aborted the connection. Usually a server somewhere else. The roles are reversed however when you implement your own server. Now you need to read the error message as "aborted by the application at the other end of the wire". Which is of course not uncommon when you implement a server, client programs that use your server are not unlikely to abort a connection for whatever reason. It can mean that a fire-wall or a proxy terminated the connection but that's not very likely since they typical...

Answer : This means the other side is using another version of TLS and you are using an older version. Set up security attribute to TLS12 before making the connection. This is a widely known problem, as many providers start using TLS12 (e.g. paypal,amazon and so on). ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12; Here is the solution, set in the registry: [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\Diffie-Hellman] "ClientMinKeyBitLength"=dword:00000200 as noted here If you are using SslStream, then you need to explicitly set the TLS version in the AuthenticateAsClient call, for example: ssl.AuthenticateAsClient(url, null, SslProtocols.Tls12, false);

Answer : Update Based on this amazing tutorial, I have put together an example project available on GitHub. It has an example for background session management. According to Apple's URL Loading System Programming Guide: In both iOS and OS X, when the user relaunches your app, your app should immediately create background configuration objects with the same identifiers as any sessions that had outstanding tasks when your app was last running, then create a session for each of those configuration objects. These new sessions are similarly automatically reassociated with ongoing background activity. So apparently by using the appropriate background session configuration instances, your downloads will never be "in flux". I have also found this answer really helpful. Original answer From Alamofire's GitHub page: Applications can create managers for background and ephemeral sessions, as well as new managers that customize the default ses...