I am running Windows Server 2012 R2, and have 2 web pages running via IIS.

The 1st one is on port 80 for HTTP, and the 2nd one is on port 16552 for an API interface.

I have opened all the connections for port 80 and 16552 for both UDP and TCP.

When connecting through a computer Windows 7 or 10 the connection works without issue each time, but when connecting through an iPhone or iPad I get "Safari cannot open the page because the server stopped responding". This only happens the 1st time. If I refresh the page it works. It will continue to work for 20 or 30 minutes, but if I wait longer than that it will require me to refresh again. Port 80 is access through Safari, and port 16552 is access through an app I created in Xcode.

Am I missing something in IIS or my firewall? I have allowed both TCP and UPD both inbound and outbound in the firewall for both ports.

When it works

When it works

When page does not load

When page does not load

  • 1
    You shouldn't need UDP for HTTP. Can you capture the packets of the ios session and see what's happening? – chicks Sep 20 '18 at 22:51
  • Yes, I just used Wireshark and ran it 2 times. On the time it failed I got about 75% failed TCP (Black with Red). When I refreshed and it worked I for 100% green with black. I am not sure how to read anymore into the packets. I'm googleing how to analyze the data now. – user1433164 Sep 20 '18 at 22:59
  • 1
    I'm going to add a screenshot from WireShark to the main post – user1433164 Sep 20 '18 at 23:01
  • You almost cannot find the cause with the information at hand. blog.packet-foo.com/2013/06/spurious-retransmissions Spurious Retransmission indicated that iOS side thought the transmission failed, while IIS did not agree. Unless you can dig out what exactly happened on iOS side (which is a black box so far), it is difficult to tell. You might try to install Firefox or Chrome on iOS though, to see if they experience the same issue. – Lex Li Sep 21 '18 at 2:05
  • I get the same results from Chrome on iOS. You say it is difficult with the information on hand. Is there anything I can do to gain the correct information, or is it not possible as the additional information would need to come from IOS? – user1433164 Sep 21 '18 at 13:48

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