The SIO_TCP_SET_ACK_FREQUENCY flag seems to be supported only on Wind…

…ows 10 Build 15063 and higher.

See dotnet/runtime#798

SimpleSocketClient/SocketConfigurator.cs

@@ -35,7 +35,10 @@ private static void DisableTcpDelayedAck(Socket socket)
             // into a future .NET version.
             // Note: On Debian-based Linux OSes, it seems TCP_QUICKACK is already enabled
             // by default (according to the man page of socket_quickack(3).
-            if (socket.ProtocolType == ProtocolType.Tcp && OperatingSystem.IsWindows())
+            // Note: On Windows, the SIO_TCP_SET_ACK_FREQUENCY seems to be supported only
+            // on Windows 10 Build 15063 and higher; on ealier Windows versions it causes
+            // the connection to fail.
+            if (socket.ProtocolType == ProtocolType.Tcp && OperatingSystem.IsWindowsVersionAtLeast(10, 0, 15063))
             {
                 try
                 {