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无法连接到端口号为2196的feedback.sandbox.push.apple.com。 打开端口（5223，2915，2916，443 ）在Windows防火墙与TCP/SSL。无法通过pushsharp中的tcp客户端连接到feedback.sandbox.apple.com
试图通过telnet连接，但没有帮助。
获取以下例外
Service Exception: PushSharp.Apple.ApplePushService -> System.Net.Sockets.Socket
Exception (0x80004005): A connection attempt failed because the connected party
did not properly respond after a period of`enter code here` time, or established connection faile
d because connected host has failed to respond 17.172.232.45:2196
at System.Net.Sockets.TcpClient..ctor(String hostname, Int32 port)
at PushSharp.Apple.FeedbackService.Run(ApplePushChannelSettings settings, Can
cellationToken cancelToken) in d:\Sample Apps\Push Notification\PushSharp-master
\PushSharp-master\PushSharp.Apple\FeedbackService.cs:line 60
at PushSharp.Apple.ApplePushService.<>c__DisplayClass4.<.ctor>b__1(Object sta
te) in d:\Sample Apps\Push Notification\PushSharp-master\PushSharp-master\PushSh
arp.Apple\ApplePushService.cs:line 51
Failure: PushSharp.Apple.ApplePushService -> The maximum number of Send attempts
to send the notification was reached! -> {"aps":{"alert":"Hello World!","badge"
:7,"sound":"sound.caf"}}
而且，这并不需要证书来连接到沙箱，那么为什么这一例外？