Connection to Server over 4G


I have a project I would like to run in a remote location.

I can connect the ESP32 to my mobile one a personal hotspot but cannot connect to the Blynk Server over 4G either the app or the ESP32.

It works fine if on a WIFI connection with internet

Any ideas?

Apple iPhone X IOS 14.6
Blynk server 80
Blynk Library V1.0.1 on ESP32

Blynk Legacy or Blynk IoT?

Does this:

mean you are using port 80?

If so then your 4G ISP may be blocking port 80 and you should try port 8080 instead.


Hi Pete,

its Blynk Legacy at the moment.


how do I change the port?

Change your Blynk.begin command to this format…

Blynk.begin(auth, ssid, pass, "", 8080);



I tried that and it does not work.

If I turn Wifi off on my phone and its just relying on cell data the App cannot connect to the server.

I am sure I tested this in the early days of designing this project and it worked fine on the hotspot

It may be that the 4G ISP is blocking the Blynk protocol, or possibly the hotspot app is blocking the traffic.