What pings iPhone to determine internet access?

Question

iPhone

Guest wifi Internet iptables is wrapped on a local server, except for dns and dhcp ports. Devices on android when typing any site open a local page. The iPhone says that "no internet" after using it without access to the Internet, it opens a page without js and pictures, links are not active. We clear the cache or private page and everything works. What pings the iPhone to determine Internet access?

Answer 1

Answering myself blog.erratasec.com/2010/09/apples-secret-wispr-req...
Request for www.apple.com/library/test/success.html.
Which answers "Success" if the Internet is working.

Answer 2

Read the C#
reference metanit.com/sharp/tutorial
How int to string etc. to avoid such questions.

Answer 3

use object[] as a parameter or dynamic, but both methods will incur a performance hit.

Answer 4

Set the AutoFlush property to true to write immediately, otherwise they write to the buffer.
But it's better to do as the manual says.

using (StreamWriter sw = new StreamWriter("CDriveDirs.txt"))
{
...
}