Fastest way to check internet connection with ESP32 Arduino

Question

Update: I know, the WIFI AP is still on & active in this case and the chip should not know about the change, but the question is still open. How should I check the connectivity?

In my project, the internet connection is really important.

After some testing, I have experienced that if I plug out the ethernet cable from my router the ESP32 still thinks, that it is still connected to WIFI, even the

WiFi.status() == WL_CONNECTED

is always true in this case.

So, I have tried out pinging google.com to examine the connection. This works but takes ages to get back the result.

How should I check the connectivity with the lowest resource cost and time?

Answer 1

Even WiFi.status() is unreliable due to the not documented details by Espressif. The API is error prone as the issues on github show.
So actually the question is . what do you really want to check? - in my definition internet connection means my line (or aerial) connectionto my ISP is unbroken. This includes

• my AP
• my router
• the ISPs fiber converter in my basement,
• the line itself and the
• ISPs gateway

This is what I use to determine wether a connection is open. I ping the IP address of the ISP gateway server. So you save time (no DNS resolution, no hops over nodes on the internet.
If you mean wether a certain service on a defined server is available, thats slow but then you are 100% sure.
Just a clarification: "ESP32 still thinks, that it is still connected to WIFI" - YES that has to be true because according to the API this ensures client to AP connection and not AP connection to some where else. Normally a good configured router informs its clients about connection loss (in this case the connected AP(s)) and these notify (depending on their config) their clients (or sometimes not or very late)