Readme: fill DNS server if setSTAStaticIPConfig

[dontsovcmc]

I think it's better to add Note about DNS if somebody want to use static IP and syncronize time (NTP) or request web servers by hostname in source code.

[tablatronix]

Could also add a debug if dns is empty, saying no dns, hostnames will not resolve or something.

Is it possible to get the dns server or assume it is gateway if unset?

[dontsovcmc]

"Is it possible to get the dns server or assume it is gateway if unset?"
https://www.quora.com/How-does-the-computer-know-which-DNS-server-to-use#
The main idea: routers has DNS-relay function, that proxies DNS requests to ISP DNS servers, obtained by router.
I think Debug message if DNS is empty needed. "Hidden magic" DNS=gateway isn't good practise.

[tablatronix]

true but typically your dns server is going to be the same one if you were dhcp.. so can we query that server and cache it etc. Does dhcp provision dns servers?

[dontsovcmc]

It's bad idea to make hidden requests to dhcp server. One of the reason of using static ip when you don't have dhcp server.

[dontsovcmc]

Here is the same problem: esp8266/Arduino#2371 (comment)

[chupocro]

"Is it possible to get the dns server or assume it is gateway if unset?"
https://www.quora.com/How-does-the-computer-know-which-DNS-server-to-use#
The main idea: routers has DNS-relay function, that proxies DNS requests to ISP DNS servers, obtained by router.
I think Debug message if DNS is empty needed. "Hidden magic" DNS=gateway isn't good practise.

A few years ago static IP worked without specifying DNS - probably the same IP as gateway was used as DNS IP if DNS wasn't specified in wifi.config()

I have some older code from 2016. and 2017. I had to rewrite for compiling it with present libraries because the devices couldn't connect to the server with the old code until I added DNS. Someone will probably confirm the IP used for DNS was the same as gateway in the old libraries.