How to pass firewall using PlatformIO espota ArduinOTA upload

ArduinoOTA’s protocol tries to connect to the host which is trying to program the device on a randomly chosen port. This often leads to the packets being filtered in a firewall since no rule exists to pass the packet and they are not related to an existing connection.

You could create a firewall rule to pass all traffic from the ESP8266/ESP32 to the programming host, but that is extremely insecure since it allows a hacked IoT device to hack your devices.

In order to fix it, add a fixed host port inĀ platformio.ini using

upload_flags = --host_port=55910

and add these firewall rules:

allow from <programming host> to <IoT device> port 55910 TCP
allow from <IoT device> to <programming host> port 55190 TCP

CompleteĀ platformio.ini example:

extends = env:d1_mini
upload_protocol = espota
upload_port =
upload_flags = --host_port=55910