Select manually WiFi or Ethernet connection for http client connection

[federico]

Hello everybody!
I am working with esp32 Ethernet kit with esp-idf v4.0
I want to create an http client to communicate with a remote server. I would like to use the WiFi connection as a primary channel to contact the remote server and the Ethernet connection as a backup in case the WiFi connection is not working.
I started from the http client example and I have added both WiFi and Ethernet connection, but I am not able to select the desired channel of comunication.
Thank you for your help